United States
Environmental Protection
Agency
industrial Environmental Research EPA-600/9-82-022
Laboratory December 1982
Cincinnati OH 45268 ^
' * '
Research and Development
r/EPA
Fourth Conference on
Advanced Pollution
Control for the Metal
Finishing Industry
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EPA-600/9-82-022
December 1982
Fourth Conference
On Advanced Pollution Control
For the Metal Finishing Industry
PRESENTED AT:
Dutch Inn, Lake Buena Vista, FL
January 18-20,1982
Co-sponsored by:
• The American Electroplaters' Society
• The United States Environmental Protection Agency
Industrial Environmental Research Laboratory
Office of Research and Development
U.S. Environmental Protection Agency
Cincinnati, OH 45268
U.S. Environmental Protection Agency
Region 5, library (PI..12J)
77 West Jackson BouJevacd, 12th Floor
Chicago, It 60604-3590
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Notice
This document has been reviewed in accordance with U.S. Environ-
mental Protection Agency policy and approved for publication. Mention
of trade names or commercial products does not constitute endorsement
or recommentation for use.
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Foreword
When energy and material resources are extracted, processed,
converted, and used, the related pollutional impacts on our envir-
onment and even on our health often require that new and increas-
ingly 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 "Fourth
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 under-
way by EPA and others to solve the pressing pollution problems of
the metal finishing industry. It is hoped that the content of these
proceedings will stimulate action to reduce pollution by illustrat-
ing approaches and techniques high-lighted by the wealth of excel-
lent 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
EPA WELCOME TO THE FOURTH CONFERENCE ON ADVANCED POLLUTION CONTROL FOR THE METAL
FINISHING INDUSTRY
George S Thompson, Jr 2
KEYNOTE ADDRESS
Bruce Barrett 3
SESSION I
REGULATORY UPDATE
STATUS OF EFFLUENT GUIDELINES FOR THE METAL FINISHING INDUSTRY AND THE GENERAL
PRETREATMENT REGULATIONS
Jeffery D Denit 6
STATUS OF EPA'S HAZARDOUS WASTE PROGRAM
Gary N Dietrich 8
SESSION II
SOLID WASTE
RCRA DELISTING PROCEDURES AND A REGULATORY OVERVIEW
Alfred B Craig, Jr 12
DETERMINATION OF THE RELATIONSHIP BETWEEN PLANT OPERATING CONDITIONS AND
WASTEWATER SLUDGE LEACHABILITY
Andrew Procko 14
OUTLOOK FOR NEW HAZARDOUS WASTE MANAGEMENT TECHNOLOGY
Robert B. Pojasek, Ph D 21
SEGREGATED NEUTRALIZATION FOR TREATMENT OF CONCENTRATED ALUMINUM FINISHING WASTES
F. M. Saunders, M Sezgm and J. M. Medero 23
HAZARDOUS WASTE TREATMENT FACILITY SITING METHODS, CONCERNS AND PROGRESS
Steven I. Taub 33
DISPOSAL: WHAT DOES IT REALLY COST?
Donald W. Smith, II and Clarence H. Roy, Ph D 43
SESSION III
PRACTICAL ALTERNATIVES FOR POLLUTION CONTROL
ENERGY, ENVIRONMENTAL AND SAFETY BENEFITS THROUGH COMPUTER CONTROLLED CURING
OVEN PROCESSES
Wilbur F. Chmery and Stephen J. Ansuini 49
OILY WASTEWATER TREATMENT BY ELECTROCHEMICAL TECHNIQUES
Delia M. Yarema 52
CROSS FLOW FILTRATION TECHNOLOGY FOR METAL FINISHERS
Han Lien Liu and James Blacklidge 55
THE APPLICATION OF ION-EXCHANGE AND MODIFIED RINSING PROCEDURES TO MINIMIZE TREATMENT COSTS
Donald W. Kemp, Ph.D 59
SESSION IV
RECOVERY
RECOVERY OF ACID ETCHANTS AT IMPERIAL CLEVITE INC.
William J Herdrich 64
iv
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RECOVERY AND ELECTROCHEMICAL TECHNOLOGY
Phillip Horelick 66
SOME SUCCESSFUL APPLICATIONS OF ELECTRODIALYSIS
William G Millmam and Richard J Heller 70
ELECTROLYTIC METAL RECOVERY COMES OF AGE
C A Swank and W J McLay 75
SESSION V
EMERGING TECHNOLOGIES AND INNOVATIVE ALTERNATIVES
NEW DEVELOI'MENTS FOR THE TREATMENT OF WASTEWATER CONTAINING METAL COMPLEXERS
C Courduvehs, Ph D, G Gallager and B Whalen 77
BATCH HYDROLYSIS SYSTEM FOR THE DESTRUCTION OF CYANIDES IN ELECTROPLATING EFFLUENTS
R G W Laughlm, H L Robey and P S Gooderham 81
RENOVATION OF ELECTROPLATING RINSE WATERS WITH COUPLED-TRANSPORT MEMBRANES
W C Babcock, E D LaChapelle and R W Baker 86
THE APPLICATION OF DONNAN DIALYSIS TO ELECTROPLATING WASTEWATER TREATMENT
Henry F Hamil 91
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Introduction
"The Fourth EPA/AES Conference on Advanced
Pollution Control for the Metal Finishing Industry" was
held in Lake Buena Vista, Florida on January 18-20, 1982.
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 and Third EPA/AES Conferences (1979 and 1980,
respectively) between key members of the EPA and the
metal finishing industry. The proceedings, contained herein,
of this Fourth 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 efforts to
effectively address the ramifications of these regulations.
Special sessions of the conference were devoted to metal
finishing solid waste, practical pollution control alternatives,
recovery technology, and emerging technologies and
innovative alternatives; reports of this work appear in these
proceedings.
The program of the conference was broken into six
segments: wastewater and solid waste regulatory status; solid
waste, regulatory overview and research; practical pollution
control alternatives, focusing on air, water, and solid waste
pollution control solutions; recovery emphasizing research
progress and field application results of wastewater recovery
technology; an open forum discussion between members of
the government and industry on regulatory reform; and a
session on emerging technologies and innovative alternatives
which highlighted several approaches such as centralized
waste treatment. Since attendees at the first, second, and
third conferences placed extreme emphasis on wastewater
and solid waste, the first segment of the Fourth Conference
was structured to provide conference attendees with a
detailed understanding of the potential impact of current
and future regulations in these two important environmental
areas. Key EPA officials, representing EPA's water and solid
waste regulatory offices, described the procedures by which
EPA prepares and promulgates regulations having a direct
impact on metal finishers.
The second segment, entitled "Solid Waste," provided the
conference attendees with an overview of the solid waste
regulations and the delisting procedure. Descriptions of
technical and administrative difficulties and solutions for
metal finishing solid waste were also presented.
Since numerous industrial plants are currently attempting
to comply with various air, water, and solid waste
regulations, the third and fourth segments of the conference
discussed practical current solutions to major pollution
problems. A majority of the presentations from these two
segments were given by industrial participants who are faced
with the burden of regulatory compliance. The latter
segment focused on recovery technology for metal finishing
wastewater.
The fifth segment, entitled "Regulatory Reform - An
Open Forum Discussion" was conducted during an evening
session. Panel members representing EPA, industry, and the
Natural Resources Defense Council individually provided
opening remarks focused at regulatory reform. The panel
then opened the floor to a free discussion in order to permit
all attendees to commonly and openly discuss the topical
subject as well as other related environmental concerns.
"Emerging Technologies and Innovative Alternatives"
was the title of the final segment. Presentations described
new developments that could eventually solve key
environmental problems. One alternative to conventional
single plant treatment, namely centralized waste treatment,
was described both technically and administratively.
This conference, attended by more than 400 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 Fourth Conference
On Advanced Pollution Control
For the Metal Finishing Industry
George S. Thompson, Jr.*
On behalf of the U.S. Environmental Protection Agency,
I cordially welcome you to this Fourth EPA/AES
Conference on Advanced Pollution Control for the Metal
Finishing Industry. For many of you, this may be the first
EPA/AES conference that you have attended; for some of
you, hopefully this is your fourth. This conference has been
structured so that while you listen and participate, your
(and our) gain in knowledge on today's environmental
issues will prove its worth in conducting your daily business
activities.
Looking back to last December, while sitting in my car
stranded in a midwest snow storm knowing that I would be
late for work, I took the opportunity to structure my
"welcoming address" thoughts to you. Obviously my initial
thoughts centered around Florida's January climate. I
consider this climatic advantage to be just a small incentive
in getting you here; the real incentive continues from our
First EPA/AES Conference in January 1978. We will, as a
unified group, discuss our mutual environmental problems
through open forum format. We will provide the latest
information on regulatory actions that affect your metal
finishing operations. We will also mutually share our
knowledge on research efforts and proven solutions to some
of our most pressing air, water, and solid waste concerns.
We have also modified our evening session; it will address a
topic of interest to each and everyone of us—Regulatory
Reform. I solicit your active participation for the next three
days. I wholeheartedly request that you not only listen, but
also constructively comment and provide the wisdom that
only you from industry possess.
I will take this opportunity to offer EPA's special thanks
to Harry Litsch, Howard Schumacher, Fred Steward, and
numerous other AES members for their continued interest
in open discussion and joint solution of our environmental
problems. I quote the following which was provided by
Mack Truck's Chairman of the Board, Mr. A. W. Pelletier,
as part of his introductory remarks at our December 1981
VOC Seminar in Allentown, PA.
"So much publicity today focuses on business
and government as adversaries, that we
sometimes overlook the real progress possible
when we both work together. . . .
Communication and cooperation must be our
guidewords for the future, because our national
and international economic strength depends
on it now more than ever."
With these statements in mind, I officially welcome you
to our Fourth Conference. Let us continue to actively and
effectively communicate and cooperate.
"George S. Thompson, Jr.
Chief, Nonferrous Metals and Minerals Branch
Industrial Environmental Research Laboratory
U.S. Environmental Protection Agency
Cincinnati, Ohio
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Keynote Address
Bruce Barrett*
I want to commend the leadership of the American
Electroplaters' Society, George Thompson of EPA and
consultant Bob Schaffer of CENTEC Corp. for their
leadership in developing this 4th Conference on Advance
Pollution Control Techniques.
We all know there have been many environmental
problems associated with regulation of this industry, and if
we continue to meet and discuss the problems, have a good
healthy debate of the issues, and continue talking to each
other, we will solve these problems. We're getting closer all
the time.
The metal finishing industry is one of the most
environmentally conscious of all industries. This is evident
by the outstanding turnout we have in this room today. I
understand that there are over 400 people here.
This morning I want to discuss some of the policies and
goals of the new Administration in EPA; some of the
regulatory issues that are of specific interest to the audience,
such as pretreatment; then close with a brief discussion of
where we are on the Clean Water Act amendments that will
be coming up in the coming weeks and months.
Administrator Anne Gorsuch, when she came into office
last year, set forth a number of priorities for the Agency. I'm
not going into all of them, but at the top of the list is to have
good science; and to have a sound scientific underpinning of
the regulatory programs that we're responsible for
implementing under the Clean Water Act. One of the
problems that EPA had in the past was that the science was
inadequate. Consequently, we would promulgate a
regulation, promptly find ourselves in court, and more
often than not come out on the short end of that litigation.
There has been a lot of wheel spinning. We now intend to
instill good scientific underpinning to our regulatory
programs. In the beginning this may add a little lead time;
however, in the long run it's going to be quicker and better
for all parties concerned. We have a new peer review system
that is going to guarantee that we get better science into our
regulations.
The Administrator also wants to emphasize delegating
more water pollution programs to the State Agencies. In the
past some of the procedures we've established have been
excessive. We want to do everything we can to get more
programs delegated to the States.
We're now considering some new compliance monitoring
strategies in our enforcement program that we think will
significantly improve our enforcement program. In the past
our inspection coverage would plow an inch wide and a mile
deep. We would go into an industrial plant and take samples
and inspect the facilities for compliance with their permit
'Bruce Barrett
Acting Assistant Administrator for Water
U S Environmental Protection Agency
Washington, D C.
and spend as long as a week or ten days taking multiple
samples. Consequently, we were not getting the kind of
inspection coverage that a good, sound enforcement
program needs, so we're going to be looking at changes in
strategy that will provide broader coverage. Instead of an
inch wide and a mile deep, maybe we'll go a mile wide and an
inch deep and focus on more inspections of shorter duration.
When we are faced with the possibility of litigation, we could
go to the more extensive inspection trips. Another emphasis
in the enforcement area is to provide more technical
assistance to the operator. Instead of a completely
adversarial process, we have to provide technical assistance
and guidance to the plant operators when they want and
need it.
We want to simplify and streamline the regulations
generally. We want to eliminate unnecessary regulatory
requirements that place an undue burden on State and local
government and on the business community. The
philosophy in the past has been: How much can we lawfully
include in the regulations? We want to look at the flip side of
that philosophy and say: What does the law require in the
regulations, and add to that legal minimum only those
additional requirements necessary to make the program
operate smoothly and effectively.
As I mentioned earlier, regulatory requirements have
discouraged, rather than encouraged, the States from
assuming the lead role in water quality management. The
need for regulatory reform is clear. We, both the regulators
and the regulated, are choking on a procedural morass of
regulations. Requirements are so burdensome and
confusing as to be counter-productive.
Our nation's water pollution control effort has been tied
up in red tape and plagued by uncertainty in a protracted
adversarial process which confuses everyone. I'll give a
couple of examples here. I'm sure most of you are familiar
with our consolidated permit regulations. That was an idea,
good in theory, but in practice just didn't work very well. It
was one of those situations where the total package turned
out to be more than the sum of the individual parts. Instead
of a one-stop shopping place for a permit for our water, air,
and solid waste programs, more confusion and regulatory
requirements were added. The resulting package was 29?
pages of fine print in the Federal Register. It would take a
Philadelphia lawyer to understand the process. We're now
revising the consolidated permit regulations and trying to
simplify, cut back, and eliminate the extraneous material.
Another area we're looking at is the water quality
standards regulations. We expect to have the proposal out
on those regulations in the next few months. Water quality
standards regulations are the foundation of any water
quality management program. When in-stream water
quality standards are established, the basis for the entire
program is because they drive everything, particularly
permit limits. We will include in the new package a use
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attainability analysis. In the past it was assumed that every
stream, every river, and every lake would meet the statutory
goal of fishable, swimmable waters. We now know that there
are some streams which, because of various physical or
environmental factors, will never be suitable for fishing or
swimming.
Another feature we're adding to the water quality
standards regulations is the benefit/cost assessment. What
does it cost to attain the water uses that you're trying to
attain? Do you want to spend that kind of money? We're
going to have a process where the States can make an
assessment of the cost and the benefits to be gained.
And finally, we're going to include site-specific criteria
development. You've all heard of the red book, which is the
water quality standards criteria document that until recently
was presumably applicable to every stream in the country.
We're developing a process now where those criteria can be
modified to meet the requirements of a given stream. Not all
streams have the same biological characteristics. There are
different fish, different aquatic plants, different organisms.
The end product will be the development of State water
quality standards that are more realistic and more
attainable.
As I mentioned earlier, we've all known for a longtime of
the dilemma faced by environmental control of the metal
finishing industry. Your industry is characterized by a lot of
small firms dealing with many toxic wastes. It has been a
serious problem. Several years ago, a very high closure rate
was predicted for the industry. As I recall now, they were
talking in terms of a 50-percent closure rate for the
electroplating industry. I think we're now seeing some light
at the end of the tunnel.
We are now considering strategies we hope will achieve
the environmental protection needed while greatly reducing
the cost of compliance. The Agency is now involved in a
major effort to review the entire pretreatment program.
We're examining a range of options that includes everything
from the existing program to applying it only to selected
industries, or to selected pollutants utilizing specific
technology, or to water quality based effluent limits on
publicly owned treatment works as a means of control using
pretreatment to address only documented problems.
Whatever program we develop in pretreatment, it is
absolutely essential to have the support of local government.
Federal and State agencies do not have the resources to
adequately control the thousands of indirect dischargers into
municipal sewage treatment plants. Only local government
has that capability. Whatever program we develop is going
to have to accommodate that fact. The program that we've
been trying to sell is too complex—it just hasn't gotten the
job done.
My personal view on pretreatment is that we should
maintain the general pretreatment standards that prohibit
the discharge of flammable materials, explosives, materials
that attack the structural integrity of sewage treatment plants
and sewer systems generally, and materials that interfere
with the operation of the plant. Local government would
then establish the pretreatment program as needed to
comply with the terms of their own permit or to protect the
quality of the sludge. The categorical pretreatment guidance
would then be available to the cities to use as necessary to
require whatever pretreatment they would need to protect
their own investment and meet the terms of their permit.
Some of these approaches are probably going to require
legislation. We need to examine what can be accomplished
within the framework of existing law and what legislative
changes may be required to come up with a workable
program.
I might mention that we had a contractor's report out f
comment and review about a month ago which examim
this whole range of options, and I sincerely hope that tl
AES and other industry groups will review that report ar
provide us with the benefit of their views on the pretreatrnei
programs. No one has a bigger stake in that than th
industry.
Touching briefly on removal credits—back in 197
Congress amended the law to provide that where public!
owned treatment works were removing toxic waste
incidental to their normal function of removing th
biological materials and solids, credit could be extended t
their industrial customers that were discharging toxi
pollutants. The problem was that the way the law wa
implemented was rather complicated, administrativel
burdensome, and required a lot of costly sampling am
analysis. Because of that a lot of cities indicated they did no
intend to grant the removal credits, which frustrated th
intent of Congress in establishing them in the first place
We're working on a revision now that will simplify thi
removal credit mechanism by establishing national remova
credits based on a study of some 40 publicly ownec
treatment works that was recently conducted by EPA. Cities
meeting minimal performance criteria will be able to gran
these credits without the extensive sampling and analysis anc
application procedures currently required. This should allow
widespread use of removal credits. The credit could provide
a significant cost savings for regulated industries. In the case
of electroplaters, it will allow some facilities to comply with
their adjusted categorical limitation through improved
operation and maintenance, thereby eliminating the need for
installation of pollution control technology.
I had the opportunity to review an editorial written by
Fred Steward in the December Journal of the AES. I
thought it was excellent. It dealt with the extension of the
compliance deadline for electroplating effluent guidelines.
Fred suggested that extension of time ought to be used
productively by looking at recovery systems, treatment
systems, and plans for sludge disposal. I want to say thai I
can second everything that he had to say in that well written
and thought-out editorial.
Let me now shift briefly to the Clean Water Act and some
potential amendments. We think the Clean Water Act is
basically a very good law. There have been a lot of problems
with the way the law has been implemented in the past but
we believe that most of these problems can be rectified by
regulatory changes—some of which I have just discussed—
and by a lot of administrative changes. Probably 95 percent
of the problems that we've had in the past with the Act can
thus be rectified. There are three or four areas that we think
may require legislative fixes. The first and most obvious, I
think, is in the pretreatment area. As I mentioned earlier,
we're looking at a range of options. Some of these may well
require a legislative fix, and I think we'll be asking Congress
to give us more flexibility in the law as it relates to
pretreatment. Before I go on, let me hasten to add that the
changes we are examining are preliminary and no final
decisions have been made at this point.
Second, we're considering a water quality waiver to the
BAT requirements. The thinking here is that if a discharger
can show that the application of BAT over and above what
he's already got in place would produce no discernible
benefits to water quality, then perhaps he should not have to
install additional treatment technology and incur the
resulting costs.
Third, we're looking at the permit life for NPDES
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permits. As you know the current time for permits is five
years. We think extending that to 10 years makes a lot of
sense.
Lastly, the 1984 BAT compliance deadline looks pretty
tough, if not impossible to meet.' We may be asking Congress
to extend that date. One method would be to extend it to
three years after fmalization of the BAT effluent guidelines.
Another method would be to go to the 1988 date Congress
just adopted last month for municipal dischargers.
That concludes my remarks. I hope you have a successful
conference, and from my examination of the program I'm
sure you will.
This paper has been reviewed in accordance with the U. S.
Environmental Protection Agency's peer and administra-
tive review policies and approved for presentation and
publication.
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Status of Effluent Guidelines for
The Metal Finishing Industry and
The General Pretreatment Regulations
Jeffery D. Denit*
As has been the situation in previous meetings, the
regulations impacting the Metal Finishing Industry have not
been finalized by the Agency. Also, as in the past, we are
pleased to be able to be here to present the best information
available and to allow you to have a preview of the Agency's
thinking. The numbers 1 am about to give you and the
options for implementing them are, at this point, only staff
recommendations.
As these recommendations move through the Agency's
approval process, it is possible that changes will be made
before they are completed. You can, however, be fairly
confident that the numbers presented will be very close to the
final version. As Mr. Bruce Barrett said, we continue to
strive for reasonable regulations and an open and
cooperative regulatory process.
In developing the upcoming Metal Finishing regulations
the Agency has responded to problem areas, and made
modifications which will make these regulations clearer and
more reasonable. The major changes in approach involve:
1. use of'Concentration basis versus Production,
2. greater coverage of total plant process wastewater
under one regulation,
3. consideration of removal which occurs at the POTW,*
and
4. separation of job shops and printed circuit board
manufacturers to account for economic impacts.
Each of the above will be discussed in detail followed by a
presentation of the staff recommendations for the regulation.
I. Concentration versus Production
The Agency has examined a wide range of Production
parameters to be used as the basis for regulation; floor area,
power consumption, area operation, etc. All had problems,
including:
1. difficulty in measuring area (i.e., one plant asked how
to measure assorted buckets of screws),
2. flow variations depending on process, product quality,
and process configuration (i.e., single stage rinse versus
multistage countercurrent rinsing), and
3. enforcement authorities, particulary POTWs, finding
product based regulations difficult.
II. Total Plant Coverage
The Electroplating regulation covered seven subcategories
which tend to cover the total process discharge at job shops.
1. Electroplating of Common Metals
2. Electroplating of Precious Metals
3. Anodizing
4. Coating
5. Chemical Etching and Milling
6. Electroless Plating
7. Printed Circuit Board Manufacturing
However, approximately half of the captive facilities have
significant wastes from other processes. This is particularly
true in the automotive industry. These facilities generally
combine wastes through one treatment system. To address
requests from industry to regulate those facilities with one
regulation reflecting combined treatment, the Metal
Finishing regulatory category was developed. The Metal
Finishing category has one subcategory and covers a broad
array of processes, including the following list.
1. Electroplating
2. Electroless Plating
3. Anodizing
4. Conversion Coating
5. Etching (Chemical
Milling)
6. Cleaning
7. Machining
8. Grinding
9. Polishing
10. Tumbling (Barrel
Finishing)
II. Burnishing
12. Impact Deformation
13. Pressure Deformation
14. Shearing
15. Heat Treating
16. Thermal Cutting
17. Welding
18. Brazing
19. Soldering
20. Flame Spraying
21. Sand Blasting
22. Other Abrasive Jet
Machining
23. Electric Discharge
Machining
24. Electrochemical Machininj
25. Electron Beam Machining
26. Laser Beam Machining
27. Plasma Arc Machining
28. Ultrasonic Machining
29. Sintering
30. Laminating
31. Hot Dip Coating
32. Sputtering
33. Vapor Plating
34. Thermal Infusion
35. Salt Bath Descaling
36. Solvent Degreasing
37. Paint Stripping
38. Painting
39. Electrostatic Painting
40. Electropainting
41. Vacuum Metallizing
42. Assembly
43. Calibration
44. Testing
45. Mechanical Plating
*Jeffery D. Denit
Acting Director
Effluent Guidelines Division
U.S. Environmental Protection Agency
Washington, D.C.
These processes generally cover all the process water
discharge at metal finishing plants. The problem of plants
having to separate wastewaters to comply with a variety of
regulations applicable to different processes has been
essentially eliminated.
HI. POTW Removal
Continuing complaints have been raised that while
POTWs remove pollutants and industry pays for this
treatment, EPA's regulations do not account for it. The
Agency did develop a procedure for POTWs to obtain
*Publica\ly Owned Treatment Works.
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removal credits. The removal credit section of both the June
26, 1978 and January 28, 1981 general pretreatment
regulations has been criticized as being so burdensome and
unworkable as to discourage sewage treatment works from
granting them.
Removal credits are a direct outgrowth of statutory
requirements. The statutory authority for removal credits is
found in a 1977 amendment to section 307 (b) (i) of the Clean
Water Act. The availability of removal credits is subject to a
number of conditions. First, and most obviously, there
must be some demonstrable removal of toxic pollutants by
the POTW. A second requirement is that the discharge from
the POTW "... not violate that effluent limitation or
standard which would be applicable to [the toxic pollutant
removed by the POTW] if it were discharged by [the
industrial source] other than through a [POTW]." A third
requirement is that the removal of toxic pollutants by the
POTW not cause the POTW to violate sludge use or
disposal requirements under section 405 of the Act. A fourth
requirement is that the POTW develop a local compliance
program.
The revised credits package, recommended for proposal
with the Metal Finishing category, does not deviate from this
basic plan. The new removal credits package simplifies and
renders more flexible compliance with the statutory
requirements. Easily the most important change is the
provision for "national removal rates." The proposal
provides that POTWs which have complied with secondary
treatment requirements, or are close to meeting those
requirements, may demonstrate consistent removal by
reliance on "national" removal rates developed by EPA,
rather than through collecting data on their individual
removal performances. Other important changes are the
elimination of the combined sewer overflow requirements
and the simplification of approval procedures. The staff
recommendations are listed below.
Pollutant
Cadmium
Chromium
Copper
Nickel
Zinc
Removal Credit
38%
65%
58%
19%
65%
(Caution: These values are based on the 25th percentile.
Industry may desire the 50th percentile values which would
result in slightly greater removal credits.)
As an example of the effect of these removal credits one
can examine Electroplating Pretreatment.
Current Pollutants
Cadmium
Chromium
Copper
Nickel
Lead
Zinc
Limits Dailv Max. (mg/l)
'1.2
7.0
4.5
4.1
0.6
4.2
After application of removal credits:
Pollutant Daily Max. (mg/l)
Cadmium 1.9
Chromium 20.0
Copper 12.7
Nickel
Lead
Zinc
5.1
1.2
12.0
IV. Separation and Economic Impact
The Agency estimated significant potential closures
among job shops and independent printed circuit board
manufacturers, 19.9 percent for job shops (3.1 percent of all
printed circuit board manufacturers, however, closures are
concentrated among independents). In accordance with the
Settlement Agreement with NAMF the Agency is separating
existing source pretreatment standards for job shops and
independent printed circuit board manufacturers from the
Metal Finishing regulations. This division essentially
amounts to a separate subcategorization of the economically
vulnerable segment of the industry. The current less stringent
Electroplating Pretreatment requirements will remain in
effect for both job shops and independent printed circuit
board manufacturers. With the installation of removal
credits, further reduction in impacts is anticipated. An
examination of effluent data from job shops indicates that
approximately 15 percent of the facilities without
precipitation/clarification will not require additional
treatment due to removal credits. This amounts to a capital
cost savings of approximately $28 million for job shops.
Even more substantial savings may occur due to plants
installing less expensive technology to meet the relaxed
values.
Finally, the following illustrates the Metal Finishing
regulation, which is based on precipitation, clarification,
cyanide destruction, hexavalent chromium reduction and
toxic organic disposal.
Parameter
TSS
Cadmium
Chromium, Total
Copper
Lead
Nickel
Zinc
Silver
Oil and Grease
Total Toxic Organics
Cvanide, Total
Concentration (mg/l)
Daily Maximum 30-Day Average
61.0
1.29
2.87
3.88
0.44
3.51
2.57
0.44
42.4
0.58
1.30
22.9
0.27
0.80
1.09
0.15
1.26
0.81
0.13
16.7
0.28
After implementation of removal credits these daily
limitations are higher than the previous Electroplating
Standards without removal credits.
Pollutants
Cadmium
Chromium
Copper
Nickel
Lead
Zinc
Dailv Max. (mg/l)
2.08
8.20
9.24
4.33
0.85
7.34
30 Day Max. (mg/l)
0.44
2.29
3.88
1.56
0.29
2.31
This paper has been reviewed in accordance with the U.S.
Environmental Protection Agency's peer and administrative
review policies and approved for presentation and publica-
tion.
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Status of EPA's Hazardous Waste Program
Gary N. Dietrich*
It is my purpose in this presentation to provide you with a
current status of the hazardous wastes regulations under The
Resource Conservation and Recovery Act (PL 94-580) and a
projection of where this program is going, particularly as it
relates to the electroplating industry. The Phase I regulations
were promulgated in May 1980 and became effective in
November 1980. These regulations contain standards
applicable to hazardous waste generators, transporters, and
owners and operators of hazardous waste treatment,
storage, and disposal facilities. Several electroplating wastes
and metal heat treating wastes are listed in the regulations.
The characteristics applicable to some unlisted
electroplating wastes may render them hazardous as well.
Two principal changes have been made since the May 1980
promulgation. First, the Extraction Procedure characteristic
was modified, with respect to chromium, so that it is now
based on hexavalent chrome rather than total chrome. The
interim final amendment, including the test procedure for
hexavalent chrome, will soon be finalized. Secondly, we have
delisted several listed wastes which contained trivalent
rather than hexavalent chrome as their principal chromium
species.
Let me give you a status report on delisting. The delisting
process is working well. It's certainly working a lot better
than I had suspected it would when first created back in May
1980. We have received 118 delisting petitions with regard to
electroplating wastes to date. We have granted temporary
delisting for 73 of those. We have denied four. Three have
been sent to their respective States which have the interim
status program, and therefore are responsible for delisting.
Eight have just been received, while 30 are presently under
review. Overall, this equates to a 97 percent average in
granting delisting petitions for electroplating wastes.
A subject closely related to the listing and delisting of
wastes is the definition of a solid waste. There has been a
great deal of confusion in the regulated community with
regard to the definition that appeared in the May 1980
regulations as it relates to wastes that are used, reused,
recycled, or reclaimed. We have been working very hard
over the last year and a half with regard to modifying that
definition and have worked extensively with petitioners in
litigation who have raised questions about that definition.
We have gone through no less than 33 drafts of a
redefinition. We think we're about at the point where we'll
have something that will better define what we intend to call
a solid waste with regard to the jurisdiction of this program.
'Gary N Dietrich
Director, Office of Solid Waste
U.S. Environmental Protection Agency
Washington, D.C
And without going into a great deal of detail let me give yo
a sense of the basic issue we're dealing with. When a waste
used, reused, recycled, or reclaimed, the jurisdiction of tr
hazardous waste program over those wastes must h
established. If wastes are burned as a fuel we woul
ultimately want to bring that under our jurisdiction.
wastes are used in a manner that constitutes disposal like
soil conditioner, fertilizer, or a deicer, we would want to ha\
jurisdiction over them. On the other hand, we do not war
jurisdiction over wastes that are recycled or reclaimed on sit
as an integral part of a manufacturing operation. To th
extent that wastes are sent off site for reclamation, we do, in
selective way, want to regulate some of those operation:
That gives you a general sense of what changes you might se
in the redefinition of solid waste. We hope to propose thi
redefinition in the latter part of March.
In the generator and transporter standards area, th
principal change that is underway is the development of
uniform manifest which would apply to interstate ani
intrastate shipments. We are working on this cooperativel
with the Department of Transportation (DOT). Thi
uniform manifest would be preemptive, in that the State
would be preempted from using any other manifest unde
DOT regulations. After the current OMB review i
completed and clearance is obtained, the package will g<
into the Federal Register as a proposed change. Of course
we would take public comment, and ultimately promulgate <
uniform manifest unless we received adverse comments. Wi
generally have worked on that issue with the States and will
an industrial interest group, principally representinj
transportation interests, and believe we have reached ;
general concurrence among the regulated community anc
the States as to what constitutes an adequate uniforn
manifest. So we have tried to do our homework and greas(
the skids for a fairly successful rulemaking.
A number of changes have been made, or are in progress.
in the interim status standards area. You may recall that, in
the fall of 1980, we dealt with the issue of whether interim
status standards would apply to wastewater treatment
processes which are handling hazardous wastes. At that
time, we proposed substituting, for interim status standards,
what amounted to a permit-by-rule which would establish
about a dozen major requirements for those types of
facilities. To enable time to complete that proposed
rulemaking without imposing the interim status standards
on those types of facilities, we suspended interim status
standards with regard to wastewater treatment processes
conducted in tanks or containers where they are connected
to an industrial process. That suspension is still in effect. We
still have yet to complete the proposed rulemaking process.
We have analyzed all of the comments and I would say in
another month or two we would be coming out with final
-------
promulgation on the permit-by-rule for those types of
facilities. For now, however, that issue is on the back burner
because we are working night and day on land disposal
standards which I'll talk about later.
Several q uestions have been recently raised concerning the
status of regulations pertinent to liquids and landfills. You
may recall that the May 1980 regulations placed a deferred
requirement that liquids in bulk form and in containers
could not be disposed in landfills after November 1981. The
rule was conditional in that bulk liquids could be disposed of
in a landfill if there was a liner and a leachate collection
system. However, with regard to containers, there was an
absolute ban. Containers containing any amount of free
liquid, even one drop, could not go into a landfill after the
November 1981 date. A number of people have questioned
that rule and it also was brought up in litigation. We
negotiated with the litigants in the September/October
period and came to a settlement in the very early part of
November. We developed a proposed rule pursuant to that
settlement. Basically, this rule does relax the requirement on
containerized liquids being placed in landfills.
It provides a formula which allocates a percentage volume
ranging from 0 to 25 percent of the landfill to be devoted to
the placement of containerized wastes having any amount of
free liquid in them. On the average, the formula should allow
about 10 percent volumetric free liquids in containerized
wastes to be placed in landfills. That's the objective we were
trying to seek. In the mean time, the ban on liquids is in effect
and we will exercise enforcement discretion with regard to
violations in this interim period, recognizing that we do have
a prosposed rule and a suspension in the process.
There was some talk that the groundwater monitoring
requirements which were also to take effect on November 19,
1981, would not take effect. They indeed did take effect and
groundwater monitoring systems were supposed to be
installed and in operation at land disposal facilities by that
date. We are soon going to be promulgating an interim rule
which would revoke the previous rule requiring submission
of an annual report. Our strategy will be to collect
information for an annual survey which will review about 10
percent, instead of 100 percent, of the regulated community
each year. This is not to say that people are relieved of
recordkeeping and recordkeeping requirements, particularly
operating plans. It is to say, however, that only those people
who are part of the 10 percent survey must submit an annual
report.
Another important change in the regulations concerns
financial responsibility. You may recall that our regulations
require proper closure of a facility, and for land disposal
facilities the regulations require post-closure monitoring and
maintenance. To assure that the monies are available for
these operations, we promulgated, in January of 1981,
financial assurance requirements that require facility owners
or operators to put money aside in a trust fund or other
instruments, such as performance bonds or surety bonds.
Since then we have been working on two other instruments
that would enable people to put money aside. One is a
financial test to self-assure that monies would be available.
This device would be principally helpful to larger
corporations with assets of more than 10 million dollars.
Another device would be an insurance policy which could be
purchased to insure that money is available to cover those
types of costs. If OM B clears the amendment providing these
two additional instrumets, we will publish this amendment
to the January regulations. The effective date of the January
regulations has been suspended to April of this year, in the
hope these additional instruments can be added before that
effective date. You probably also have read that this
Administration is about to propose a suspension of the
liability insurance requirements which were also
promulgated on January 12, 1981, and which were to take
effect in July of last year. We have received OMB clearance
with regard to a proposed rule to that effect. The rule, which
will be out in about another 30 days, will propose
elimination of liability insurance for treatment, storage, and
disposal facilities. We will take public comment on this rule
and, based on those comments, determine whether to go
through with that suspension. I think those are the major
changes affecting the Phase I regulations.
Phase II regulations set the standards which are to be used
in permitting treatment, storage, and disposal facilities. In
January, 1981, we promulgated the Phase II standards
governing storage, treatment and incineration. We also
promulgated on February 13 a temporary standard
governing the permitting of new land disposal facilities and
on February 5 reproposed regulations dealing with the
permitting of existing land disposal facilities. The regulations
dealing with storage, treatment, incineration, and new land
disposal facilities did indeed go into effect in July and
August. The Agency will be using these regulations to call in
Part B applications with regard to existing facilities and to
write permits for those types of facilities. The standards for
existing land disposal facilities are still in a proposed stage,
but we were recently ordered by the District Court of the
District of Columbia to promulgate those standards by
February 1 of this year. We think that we have a reasonable
and workable standard that can be promulgated for existing
land disposal facilities. I do not think that we can physically
make the February 1 deadline, but believe we can complete
this task sometime between March 1 and April 1. We indeed
are going back to the Court to ask for a reconsideration. As I
say, 1 think we have a standard that will be workable. I can't
give you all the details of that standard because I would be
violating ex parte. 1 can, however, give you an indication that
the standard is likely to be an environmental performance
standard. It will not require that arbitrary retrofitting of
existing land disposal facilities as would technology-based
standards, which was one of the principal criticisms we
received from the regulated community with regard to a
previous proposal on land disposal facilities.
Given that we have the regulatory program in place, how
does regulatory reform affect the hazardous waste program?
There are two things in regulatory reform that we are
responsible for dealing with. One is the Executive Order
12291 which essentially requires that those regulations that
were not effective the date this Executive Order was issued
should not go into effect until a complete regulatory impact
analysis had been done. Principally, that affected the Phase
II regulations, promulgated in January and February
concerning the permitting of storage, treatment,
incinerators, and new land disposal facilities. However, this
Executive Order indicated that we could allow the Phase II
regulations to go into effect without a regulatory impact
analysis if there was good cause to do so. We indeed did do
that. The cause was that we were under a court order in the
first place to promulgate those regulations.
OMB approved this action, but with the condition that we
would perform a regulatory impact analysis on those
standards during calendar year 1982, and that we would
subsequently proceed with any amendments that are
indicated by that analysis and ultimately finalize the
standards during calendar year 1983. So to simplify it, the
storage, treatment, and incinerator standards which are in
effect today will go through a regulatory impacts analysis
-------
du¥ing this calendar year. Some amendments will probably
be added before the standards are finalized toward the end of
1983. The situation is basically going to be the same for land
disposal standards. In promulgating those standards to meet
the February 1 court order, we will establish a standard
without going through the regulatory impact analysis. We
will do the regulatory impact analysis after the fact and
produce the changes deemed necessary by that analysis
before the end of 1983. In essence, we hope to have, if you
will, all of our standards in final form by the end of 1983. In
the interim, these standards will be used for both permitting
and authorizing states.
Now I would like to direct my discussion toward the
possible results of the places in our regulations where we can
tailor the regulatory requirements to deal more carefully
with the degree of hazard by lessening requirements for those
wastes which are less hazardous than others and increasing
requirements for those wastes that produce a particular high
degree of hazard. A tailoring of the technical requirements of
our regulations, both in the storage and treatment areas, as
well as in the land disposal area will occur. With regard to
land disposal, some wastes are hazardous because they fail
the EP toxicity characteristic. However, in some cases, these
wastes are not codisposed with organic wastes; in addition,
they may pass a neutral-water EP toxicity test. In these
situations, we think some lesser requirements can be applied.
Some examples of such wastes are foundry wastes. We
believe a great many foundry wastes could pass a neutral-
water E P test and are not co-disposed with municipal wastes,
but instead are "monofilled." We believe we can give a lesser
set of requirements to these types of wastes. A liner or
leachate collection system will probably not be required. The
cover requirements at closure could probably be lessened.
Another example of tailoring the technical requirements of
our regulations concerns facilities that neutralize wastes
which are hazardous solely because of their corrosivity.
Again if that neutralization takes place relatively soon,
we believe requirements for lining and groundwater
monitoring may not be necessary. Finally, with respect to
storage facilities, if a waste is hazardous only because of its
metal content, and is a non-liquid waste, we're not quite sure
that you need secondary containment, some of the
inspection programs, or some of the contingency plans that
would otherwise be required of other types of hazardous
wastes. So that gives you two examples of some of the
tailoring we are considering.
On the other end of the scale, however, we may develop
more stringent requirements for land disposal of certain
wastes. We might ban the disposal of certain highly toxic or
persistent solvents from land disposal.
Another area that we're looking at is the class permit.
Those who follow the water program may be familiar with
the general permit used in the 404 dredge and fill program.
This would be a similar type of permit. Instead of trying to
permit individual facilities, we would try in some cases to
permit a number of facilities which have some commonality.
In doing this we would reduce a lot of the permitting
paperwork, both on your part and on the permittee's part,
and therefore save time and frustration for all concerned. We
are working very hard to develop a set of class permit
procedures that would go into the consolidated permit
regulations. We are hopeful that we can get those procedures
developed and proposed in late February or early March. In
some sense, coming up with a class permit procedure may be
the most meaningful thing we are doing in the regulatory
reform area.
While we're doing all of the foregoing activities, we will
continue the fine-tuning of our regulations as we see rna
problems crop up that should be dealt with to make t
program workable. For instance, we are soon going to coi
out with a set of amendments to take care of some of t
problems concerning our incinerator standards so t
program can work effectively.
Three other areas that I should address are statute
changes, state authorization, and consolidated pern
regulations. The Resource Conservation and Recover}' A
comes up for reauthorization this year. Reauthorization
appropriation authority usually provides an opportunity
make changes to the statute. At this point, the Agency do
not intend to ask for substantive changes to the statute tl
year. The predominant thinking is to try to make tl
program work with our current statutory authority, to g
the regulations out and have them become effective, and
go through the regulatory impact analyses before we tink
with the statute. At the end of that time, if real reason fi
statutory change exists, we will then go in for changes. I ha'
a suspicion that Congress is not particularly interested
dealing with statutory changes in the RCR A during this ye;
either since they have other major problems to deal with sue
as the Clean Air Act and the Clean Water Act.
Most people are aware that the statute enables us am
indeed, encourages us to authorize the program to tl
States. We are doing that and it is a high priority for th
Agency, for this Administration. Currently, we have 2
States that have been authorized for Phase I of the progran
We hope that the number will move up to the 35 to 40 are
before the end of this year. No States have yet bee
authorized for Phase II, however, most of the States ihi
now have Phase I are expected to come in for Phase II. W
think the Phase II authorizations will lag those of Phase I b
about 1 year. 1 mentioned earlier that in meeting th
February 1 court order, we would have put our las
regulation in place. Therefore we would be in a position t
begin the timeclock for full authorization of the States rathe
than interim authorization of the States. That decision ha
not been made, but it is a decision that is likely to b
considered within the next 30 to 45 days. The inclination o
the Agency at this time as far as I know, with all regulation
in place, is to allow the States to have the option of goinj
directly into full authorization by the fall of this year.
Lastly, there are several changes developing in the area c
the Consolidated Permit Regulations, which cover RCR/
and other permits. These changes are the result of th
settlement of litigation. Negotiations took place in the sprin
and summer of last year and culminated in a settlemer
around September. There are some 24 changes in tha
settlement that affect the RCRA permit regulations whic,
are part of the consolidated permit regulations. I will add res
the three most important ones. The first involves a change ii
the requirements for modification of interim status
Basically, what we're saying there is that we would allov
interim status land disposal and incinerator facilities t<
expand up to 50 percent, and storage and treatment facilitie
could expand an unlimited amount, without having to firs
obtain a new permit. Another is to change from a 10 yea
RCRA permit to a lifetime RCRA permit. In doing this
however, we have asked for more reopener clauses
particularly the ability to reopen a permit if there is z
significant change in our regulations. And finally there was
an amendment that would deal with the so-callec
construction ban. Currently, new facilities cannot begir
construction until they have a RCRA permit. The change
would relax that with regard to storage, treatment and
incinerator facilities and allow construction to begin without
10
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a permit but, indeed, require a permit before operation in the Federal Register within the next couple of months. I
begins. However, with regard to land disposal facilities, a think that covers the essential items of the status and
permit would be required before construction begins. These direction of the hazardous waste regulatory program at this
are the three most important items resulting from the NRDC time.
settlement concerning the consolidated permit regulations. This paper has been reviewed in accordance with the U.S.
Those changes will need to be proposed and go through the Environmental Protection Agency's peer and administrative
proposed rulemaking before they are promulgated. We review policies and approvedfor presentation and pub //co-
would expect that those proposed rules would be published tion.
11
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RCRA Delisting Procedures
And a Regulatory Overview
Alfred B. Craig, Jr.*
INTRODUCTION1
EPA has promulgated regulations designed to manage
and control the country's hazardous wastes from
generation to final disposal. These regulations are a result of
a directive to EPA by Congress in the Resource
Conservation and Recovery Act (RCRA) of 1976 (Public
Law 94-580). Congressional concern was prompted by the
large quantities of solid wastes being generated.
The RCRA regulations are to control activities of
generators, transporters, treaters, storers and disposers of
hazardous wastes. They differ from those regulations
concerned with air and water pollution in that air and water
regulations vary according to the specific industry (for
example, electroplating) to which they are directed. In
contrast, all industries that generate, store, haul, or dispose
of hazardous wastes must comply with the same sets of
rules. Most owner/operators of electroplating facilities will
be considered generators of hazardous wastes and may be
considered to own or operate treatment, storage, or
disposal facilities. The procedures to determine if wastes are
hazardous and the requirements for generators, storers, and
disposers of hazardous wastes follow.
Identification of Hazardous Wastes
Under the Hazardous Waste and Consolidated Permit
Regulations promulgated on May 19, 1980, solid wastes
include all substances destined for disposal and not already
regulated by the Clean Water Act or the Atomic Energy Act
of 1954.
EPA has developed the following methods of listing
wastes as criteria for determining which solid wastes must
be classified as hazardous. A waste may be listed in the
Federal Register, it may be tested and determined
hazardous, or the generator can admit that it is hazardous.
Tests for: Ignitability
Corrosivity
Reactivity
Toxicity of leachates
are used to list or delist wastes. A waste possesing one or
more of these traits will be declared hazardous.
'Alfred B Craig, Jr.
Nonferrous Metals & Minerals Branch
Industrial Environmental Research Laboratory
U.S. Environmental Protection Agency
Cincinnati, Ohio
The following electroplating wastes are listed as
hazardous unless proven otherwise:
Wastewater treatment sludges (toxic)
Spent plating bath solutions (reactive, toxic, & corrosive)
Sludges from the bottom of plating baths (reactive, toxic,
& corrosive)
Spent stripping and cleaning bath solutions (reactive,
toxic, & corrosive)
The corrosivity criterion is used to determine if these
materials can extract toxic contaminants from other wastes
or make them soluble. A material is corrosive if it has a pH
below 2 or above 12.5, or if it corrodes steel (following a test
developed by the National Association of Corrosion
Engineers).
Reactive wastes have one or more of the following
tendencies:
To autopolymerize
To create a vigorous reaction with air or water
To exhibit thermal instability with regard to shock or to
the generation of toxic gases
To explode
The final characteristic, toxicity, is one of most
importance to electroplaters. If disposed of improperly,
toxic wastes may release toxic materials in sufficient
amounts to pose a substantial hazard to human health or to
the environment. EPA has designed a leaching test (called
the Extraction Procedure) to measure the amount of toxic
materials that can be extracted from the waste at a pH of 5,
during a 24-hour period, with constant stirring. If the
extract obtained from the test exceeds set limits for certain
contaminants, the waste will be considered hazardous.
Eight metals are among the 14 materials selected as toxic;
Table I
Toxic Waste Limits Set by EPA's Extraction Procedure
Pollutant Extract level (mg/L)
Arsenic 50
Barium 100.0
Cadmium 1.0
Chromium 5.0
Lead 5.0
Mercury 0.2
Selenium 1.0
Silver 5.0
SOURCE: U S Environmental Protection Agency, "Hazardous Waste
Management System Identification and Listing of Hazardous Waste," Pt 3, Federal
Regiuer. 45(98)33084-331.13, May 19, 1980
12
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several of these metals are commonly used in electroplating.
Table I lists the specific metals with the standard for each.
Other materials may be added to the list in the future.
Requirements for Hazardous Waste Generators
Producers of hazardous waste are considered generators
under the regulations. It is a generator's responsiblity to
determine if the waste is hazardous by 1) consulting the lists,
2) conducting EPA-specified tests, or 3) the generator may
simply declare the waste hazardous. If the waste is known
to be nonhazardous, testing is not necessary; however, the
generator is responsible for the accuracy of that
determination.
Generators of hazardous wastes are responsible for
notifying EPA of their activities, using appropriate
containers, labeling the containers, and ensuring proper
disposal. The law also requires generators who produce and
dispose of more than 1,000 kg (2200 Ib) of hazardous waste
per month, with certain exceptions, to use a manifest system
to ensure proper transport and disposal.
The manifest records the movement of hazardous wastes
from the generator's premises to an authorized off-site
treatment, storage, or disposal facility. The manifest, signed
by the generator, transporter, and disposer, is an official
record that all Department of Transportation (DOT) and
EPA requirements have been met. The generator must
maintain original copies for 3 years, and must report to
EPA if the manifest is not returned in 45 days documenting
its arrival at its approved destination.
Exception reports are required, listing any unreturned
manifests. Annual reports, documenting shipments of all
hazardous wastes originating during the report year, also
are required. In general, all information submitted by a
generator is available to the public to the extent authorized
by the Freedom of Information Act and EPA regulations
associated with that act.
Requirements for Treatment, Storage and Disposal
Facilities
When wastes are stored on site for 90 days or longer, the
generator falls under an additional set of regulations
designed to control owners and operators of hazardous
waste storage and disposal facilities. The standards for
storage promulgated in May 1980, are intended to prevent
the release of hazardous wastes from storage areas into the
environment. Hazardous wastes must be stored in tanks
and containers that meet specifications established by EPA
for the storage of flammable and combustible liquids.
Beyond these specifications, materials compatible with the
hazardous wastes must be used to construct or to line the
containers.
Storage areas must have a continuous base impervious to
the material being stored and must be designed for spill
containment with either dikes or trenches, which require
daily visual inspection. Throughout the storage period,
records must be maintained showing the identity and
location of all stored hazardous wastes. Site selection
requirements apply, and leachate monitoring may be
required. Obviously, it is an economic advantage not to be
classified as a storage facility by default.
As stated earlier, these standards only apply to those who
store hazardous wastes for 90 days or more.
Information Requirements for Temporary Exclusion of
Electroplating Wastes
It is possible for a waste generator to petition to EPA for
an exclusion of his waste from RCRA's hazardous waste
requirements. If granted, then they are not considered
hazardous. The applicant must submit the following
information to the Administrator of EPA:
(1) Description of the manufacturing processes which
produced the listed waste.
(2) Description of the waste treatment system (including
chromium reduction, cyanide destruction,
neutralization, flocculants added, etc).
(3) Schematic diagram of the waste treatment system.
(4) Average and maximum volume/tonnage of waste
generated per month and per year.
(5) Disposal scenario used for waste generated prior to
November 19, 1980, and the scenario proposed for the
waste if an exclusion is granted.
(6) Total constituent analysis of the sludge (complete acid
digestion) for each of the EP toxic metals and nickel.
(7) Analysis of the sludge for total cyanide. If the
concentration recorded is greater than 1 ppm, test the
sludge for free cyanide. If cyanide is used in the
manufacturing process, a minimum of four samples
should be tested. If cyanide is not used, the test result
from one sample is sufficient.
(8) EP toxicity test results for cadmium, hexavalent
chromium, and nickel. Test results should be
submitted on samples obtained over a period of time
to address any variability of constituent concentra-
tions in the sludge (a minimum of four samples
analyzed to this effect are required).
(9) EP toxicity test results for cyanide. Test results should
be submitted using the EP extraction procedure but
substituting distilled water for acetic acid.
(10) All EP toxicity tests should be performed using the
method of standard additions. All recovery results
should be reported.
(11) Explain any data point that deviates from the range
identified by the other reported analyses.
(12) For each constituent not utilized in electroplating
operations, the results from one total constituent
analysis and one EP test should be submitted. In
addition, a statement that these constituents are not
used in the process is required.
(13) Information requirements as specified in 40 CFR
260.22(i) 1-12 (omit #7). This requirement applies to all
inorganic wastes.
The generators petition must refute all of EPA's reasons
for listing the waste. It is important to note that delisting of
a generator's waste stream was not intended as a panacea
for "compliance" with RCRA. Those plants with truly
hazardous wastes will remain in the system. It was intended,
however, to exclude those companies which, because of the
procedural or definitional requirements of the regulations,
had been inadvertently or incorrectly included in a
regulated category. These companies may petition for an
exclusion because their wastes truly are non-hazardous.
The EPA's hot line number is 800-424-9346 (202-382-
3000 where RCRA questions can be answered.
This paper has been reviewed in accordance with the U.S.
Environmental Protection Agency's peer and administra-
tive review policies and approved for presentation and
publication.
'Environmental Regulations and Technology The Electroplating Industry, EPA
625/10-80-001, August 1980
13
-------
Determination of the Relationship Between
Plant Operating Conditions and
Wastewater Sludge Leachability
Andrew Procko*
INTRODUCTION
A recent study1 conducted cooperatively between the
American Electroplaters' Society (AES) and the Industrial
Environmental Research Laboratory, U.S. Environmental
Protection Agency (EPA) evaluated the leaching characteris-
tics of sludges generated by electroplating wastewater treat-
ment systems. In this study 12 plants' sludges were character-
ized. One of the recommendations resulting from this work
was to further investigate what effect the primary operating
variables of the treatment system had on both the effluent
quality and the leachability of heavy metals from the
sludges. This paper presents the results of such an investiga-
tion.
Untreated wastewaters were collected at the plant and
shipped to the laboratory where they were subjected to a
number of treatment tests in which the treatment chemicals
and pH were varied. Metal concentrations in the effluent
and sludge extract were monitored.
The goal of this research was to characterize operations
and sludges from six plants carrying on a wide variety of
plating operations so that the information developed would
be applicable on an industry-wide basis. The six plants were
selected from the 12 that had participated in the EPA-AES
study mentioned above.
DESCRIPTION OF PLANT, PLANT PROCESSES,
AND SAMPLING
Plant Selection Criteria
Selection was based on the variety of metals utilized, the
wastewater treatment system, and the leaching
characteristics of the plants' sludges. The presence of
cadmium in the plants' wastewaters was highly desirable as
cadmium appears to be a problem metal with regard to its
leaching characteristics. The plants designated as 2, 3, 4, 6, 7
and 8 were selected for this study, as previous testing had
shown significant quantities of Cd, Cr, Ni, Zn, Cu, and Al
present in wastewaters and sludge from these facilities. Other
contributing factors included: good cooperation from plant
management and the fact that the plant sludge had metal
levels that EPA would consider hazardous based on results
from the EPA Extraction Procedure (EP). The limits above
which EPA considers EP results as hazardous are shown in
Table 1.
Cyanides were oxidized at three plants with either
sodium hypochlorite or chlorine in an alkaline
environment. The treated chromium and/or cyanide waste
streams were then combined with the other acid / alkali waste
streams where pH adjustment with lime occurred in most
plants. Generally, all six plants had their pH set-point at 10.
Four plants added flocculating agents to the combined
wastewaters to improve settling of the metal hydroxides in
the clarifier. Overflow from the clarifier was discharged to
the plant sewer while underflow went to further thickening
and/or dewatering before disposal.
Two plants were using integrated treatment at the time of
this study. The chemical treatment of the rinse water was inte-
grated into the operation of the plating line. Integrated treat-
ment involved continuously treating rinse waters during, or
immediately after, the rinsing process. One plant had a
treatment tank and feed sump corresponding to each rinse
tank. The rinse water was continuously circulating from the
rinse tank to the sump to the treatment tank and back to the
rinse tank in a completely closed-loop fashion. Water was
added only when required to adjust the tank level. The
continuous treatment of the rinse water produced increasing
quantities of metal hydroxides that were recirculated back to
the rinse tank. The metal hydroxides were settled out daily
and transferred to another settling tank, and finally filtered.
Another plant used integrated treatment for its CdCN rinse
water. The cyanide rinse tanks were used as the first stage of
cyanide oxidation. A slip-stream of this treated rinse water
was combined with all other cyanide rinse waters and sent
through a second stage of cyanide oxidation, and then
further treatment.
Sample Collection
During the preliminary study mentioned earlier, detailed
Table 1
Maximum Concentration of Metals for
Characteristic EP Toxicity
Metal
As
Ba
Cd
Cr
Pb
Hg
Se
Ag
Maximum Concentration (mg//)
50
IOOO
10
50
50
02
10
50
*Andrew Procko
CENTEC Corporation
Reston, VA 22090
1 Weit'diih. J H. \1i(.'arth\,J I ami Prixko, I , kinIroplatmg WaMe»ater Slui/gt
Chaiaueniaiwn i:P-i-6(MI'S2-lU-(IM. C.S Environmental Pmteuum Agent \,
( innnnan. Ohm, 1981
14
-------
plant data were not collected. Therefore, a 1-man
presampling survey was required to identify the plating
operations; type and quantity of rinses, potential sampling
sites; number of samples required; and the operating
procedures and chemicals for the wastewater treatment
system. After completion of a sampling plan for each of the
plants, a sampling team of one or two men, depending on
the size and complexity of the plant, visited each plant,
noted the flow rates of individual streams where necessary,
and observed operations for anything unusual.
Liter samples were taken in order to allow for an
evaluation of the performance of individual subsystems,
such as chrome reduction, and the overall Wastewater Treat-
ment System (WWTS). As it was impossible to collect an un-
treated sample of a plant's combined wastewater, the indivi-
dual wastewater samples were combined in the laboratory in
proportion to their relative flow rates in the plant. Fifty-five
gallon drum samples to be used in the experimental program
were taken of all wastewater streams at locations upstream
of the plant's pH adjustment system.
For the six plants studied, the underflow from the plants'
clarifier was sampled, as this would represent the feed to a
mechanical dewatering system if one were present. For this
study, it was decided that samples of underflow directly
from the clarifier would more closely resemble the more
general case of metal finishing treatment sludge than would
sludge from a thickener or from a dewatering device. The
underflow characteristics would then be used as a basis of
comparison for the results of the testing program.
Retention times and flowrates for each treatment step
were calculated from data obtained in the plant. If
capacities of waste treatment tanks were not readily
available, tank measurements were made by the survey
team. Flowrates were confirmed by several methods. These
include: counting rinse tanks and measuring overflow rates,
including some allowance for cooling water, condensate,
sanitary water, etc.; reading water meters when available;
and measuring the inflow and outflow of wastewater
sumps. From flowrates and tank capacities the retention
times were calculated. Table 2 contains the analytical test
results for actual plant samples.
Plant Operations
Plant 2 is a captive shop which uses chromate dips and
plates acid Zn and acid Cd onto metal screws. One barrel
line is present in the plant and serves both plating tanks.
Plant 3 is a job shop which barrel and rack plates
cadmium and copper, as well as using solder and chromate
dips.
Plant 4 is a job shop which plates Cu, Ni, and Cr onto
zinc die-castings. One manual rack line is present in the
plant.
Plant 6 is a captive shop which plates nickel and chrome
onto steel. One automatic rack line is used for plating, and
one manual rack line is used for stripping.
Plant 7 is a job shop which plates brass, bronze,
cadmium, chromium, copper, nickel, and zinc. The plant
also anodizes and bright dips aluminum.
Plant 8 is a job shop which plates copper, nickel, and
chrome onto plastic. The system is composed of one
manual rack plating line. Plating onto plastic requires that
Sample
Description
Yellow Chromate
Zinc Bath
C admium Bath
Acid Bath
Effluent
Spent Acid
Blue Chromate
Sample
Description
Clear Chromate
Yellow Chromate
CdCN Rinse
Other CN Rinse
Acid Rinse
After CN Oxidation
After pH Adjustment
Effluent
Centrate
Clarifier Underflow
Acid Sump (Barrel)
Acid Sump (Rack)
After CN Oxidation
'Dissolved Mcldl
Analytical Test Results
pH TDS TS
1 59 28.000 35.100
543 168.200 270.000
1 98 87.500 99.500
074 7.760 12.500
11 15 16.100 16.100
1 72 2.530 4.920
062 27.300 31.300
PH ro Y TS
7 18
1238
1276
1081
11.97
11.22
1090 4.430 5,640
11 75
10.43
10.36 5,940 10,700
10.86
4.32
1076
Table 2
for Actual
Plant 2
Cd
254
037
14.600
372
368
037*
3X6
094
Plant 3
Cd
3,980
0.91
—
605
54.5
—
69.5
2.90
1.68*
104*
538
106
246
Plant Samples (mg/l)
o-' 0"
19.070 770
<0 1
849
1 57
6 08 0.08
020*
66 8 <0 05
343 74
Cr' Cr*
2.02 <0.05
705 685
45.8
14.9
10.5*
14.6*
3.55 1 52
1.46
252
Zn
3,020
22.500
1.850
645
773
066*
499
2.580
Zn
0.82
0.51*
442*
CN Cu
2987
42 2 2 70
11 4
31
2.18
1.58*
5.17
076
0.09
15
-------
Table 2
Plant 4
Sample
Description
Heated Cvanide
Alter pH Adjustment
Etlluent
hilt rate
Treated Cyanide
Ni Rinse
Cleaner Rinse
Sludge
Sample
Description
After Mix Tank
Clanfier Overflow
Effluent
After CR Reduction
Combined Acid Rinse
After Mix Tank
Sludge from Clanfier
/>H
1007
1207
II 70
II gg
1001
7.32
9.13
1066
pH
11 56
11.80
9.79
193
263
12.36
11.78
TS TDS
\ 38.000 X.200
TS TDS
5,250 2,000
81,100 1,940
Cr1
1 33
1 51
092*
1 30*
062
209
034
158
Plant 6
Cr'
<0.5*
<0.5*
<05
<05*
352
45.6
l.ll
45.6
Cr*6
<005
<0.05
<0.05
<0.05*
<0.05
<0.05
<0.05
<0.05
Cu
423
1 15
0 11*
1 41*
806
657
075
349
\i Zn
31 1
265
096*
2.43*
158 036
165 259
0 33 25 0
55 3 25 0
Ni
<0.1
<0.1
<0.l
<0.l*
2.59
18.5
0.35
18.5
CNdli.")
575
<002
<()02
Plant 7
Sample
Description
Acid Alkah
Acid /Alkali
Untreated Cr
Treated Cr
Untreated CN
Untreated CN
Treated CN
Untreated Al
Combined Streams
Clanfier Effluent
Clanfier** Underflow
Underflow Sludge Bed**
Sample
Description
After pH Adjust
Clanfier Overflow to Effluent
Filter Filtrate to Effluent
Chromium Waste
Acid/ Alkali Rinses
Clanfier Sludge**
*Dissolved metal.
pH
671
688
223
1 55
7.69
12.13
3,26
2.41
8.5
10 1
8.53
pH
964
9 16
9.45
2 14
3.22
9.84
**Metal concentrations are those found
TS TDS CJ
1.080 0 10
994 006
810
-------
duced a sludge with the best leaching characteristics without
reducing effluent quality.
Plant simulation and treatment studies were also
performed using 55-gallon drum samples of the individual
waste streams collected at each plant.
SIMULA TION STUDY
Samples of the individual waste streams in each plant
were taken. These samples were combined in ratios
proportional to their flow rates in the plant to simulate the
plant's untreated wastewater. This simulated wastewater
was treated under conditions as close to plant conditions as
possible. The plant's chemicals were used for pH adjust-
ment and flocculation, and residence times in the pH adjust-
ment tank and clarifier were duplicated in these simulations.
Following settling, the supernatant was decanted. This
sample, the simulated overflow, was analyzed for metals of
interest and compared to the plant's effluent sample.
The simulated overflow was collected, extracted by the
ASTM-A extraction procedure, analyzed for metals and
compared to the ASTM-A extract of the plant's clarifier
underflow. Good agreement between simulation experi-
ments and actual plant samples suggests that results of sub-
sequent laboratory treatment studies will be meaningful in
the plant operating environment. Data are recorded in Table
3.
FLOCCULATION STUDY
Additional studies were conducted on portions of the
simulated waste stream of each plant to determine an
optimum polymer flocculating agent and its effective
concentration. In this study, four anionic polymer
flocculating agents were evaluated against the flocculating
agent employed at the plant to determine which produced
the best settling rates and flocculant characteristics. Since
this was not intended to be a major area of this investigation
the flocculating agent chosen and its optimum
concentration were used throughout the remainder of the
study. The results of this study were qualitative and are
shown in Table 4.
Settling tests were performed by evaluating each
flocculating agent over a concentration range of 0 (blank) to
8 mg/1.
Plant 2 used no polymer flocculating agent. Magnifloc
836A and Calgon WT-3000 performed well on its simulated
waste stream. Magnifloc 836A was effective at a much
lower concentration and was chosen for future studies.
Plant 3 also used no polymer to aid settling in their
treatment. Very slow settling rate was observed without
added flocculating agents. Only Calgon WT-3000 resulted
in improved settling and floe characteristics. It was effective
at a final concentration of 0.5 mg/1.
Plant 4 settled well using Separade P-3 (its own choice of
polymer), Separan AP-273 and Calgon WT-3000. Separan
AP-273 was chosen since it was effective at the lowest
concentration.
Plant 6 used 6 mg/1 Percol in its treatment. Percol was
found to be effective at 2 mg/1. This was the only plant in
which its flocculating agent outperformed the others
investigated.
Plant 8 used EPEC Floe 306 which performed well at 5
mg/1; however, Separan AP-273 and Calgon WT-3000
were equally effective at lower concentrations. Separan AP-
pH
Plant
Underflow
(ASTM-A) 10.36
Plant
Simulation
Underflow
(ASTM-A) 10.9
Plant
Simulation
Underflow
with Correction
for Dilution
Plant
Effluent*** 11.75
Plant
Simulated
Effluent"* 10.9
pH
Plant
Underflow
(ASTM-A) 10.66
Plant
Simulation
Underflow
(ASTM-A) 10.5
•Correction Factor Cannot be Applied.
•"Analysis was for dissolved metal rather than
Table 3
Results of Plant Simulation Tests
Plant 3
TS DS Cd OT Crtk Cu Ni Zn
10,700 5,940 0.04 095 1.39 0.17 <0 1
11,000 4,450 033 Oil 0.80 1.00 <0 1
0.55 0.18 1.34 1.67 *
1.68 10.5 158 <02 051
0.03 17.9 4.73 <0.l 0.05
Plant 4
TS DS CN O1 t>+6 Cu Ni Zn
138,000 8,200 <0.02 0.41 0.49 006 038 <0.l
58,100 — — <0.l <0.05 2.05 1.96 0.02
total metal to determine the effectiveness of treatment.
17
-------
I'H
Cr1 Cr*6
Cu
Ni
Plant
Simulation
Underflow
with Correction
for Dilution
Plant
Fflluent***
Plan!
Simulated
rffluenl***
Plant
Underflow
(ASTM-A)
Plant
Simulation
Underflow
(ASTM-A)
Plant
Simulation
Underflow
with Correction
lor Dilution
Plant
Effluent***
Plant
S\mulated
Flfluent***
Plant
Underflow
(ASTM-A)
Plant
Simulation
Underflow
(ASTM-A)
Plant
Simulation
Underflow
with Correction
for Dilution
Plant
Effluent
Plant
Simulation
Effluent
Plant
Underflow
(ASTM-A)
Plant
Simulation
Underflow
(ASTM-A)
Plant
Simulation
Underflow
with Correction
for Dilution
Plant
Effluent***
Plant
Simulated
Effluent***
II 7
105
092
1.10
6 86 6 56
Oil 0 96
Zn
0.07
Plant 6
TS DS
1 78
II 70
81,100
29.800
1,940
3,840
1.80
70
Cd
.02
<.02
Cr'
<.05
Plant 7
Cu Ni
984
950
.25
.20
TS
11.900
11,500
.04
.06
0.16
.10
.04
Plant 8
DS
2.400
3,370
.38
0 23 0 09
Cr1
1 12
0 19
039
<050
<0 10
Zn
.65
080
100
Cr*6
<0.05
<0.05
<0 10
<025
1.42
3.77
3.6
6.90
Cr1
0.14
0.37
2.88
1.01
Cr*6
<005
<005
<005
<005
TS
7,774
4,375
<0 10
<025
DS
2,074
2,080**
0.08
<005
Ni
020
0 10
003
9 16
95
022
088
1.09
079
055
*Correction factor cannot be applied
"After settling for 2.25 hours
"After settling for 2.25 hours
***Analysts was for dissolved metal rather than total metal in order to determine the effectiveness of treatn
18
-------
273 was effective at 2 mg/1 and was throughout further
studies.
TREA TMENT STUD Y
Test Plan
Treatment studies were conducted to determine the effect
of treatment chemical and pH on the effluent quality and on
the leachability of the sludges produced. The method
utilized to achieve these goals was to take actual untreated
electroplating wastewaters and treat them with three
common precipitation chemicals: sodium hydroxide
(NaOH), soda ash (Na2CO3), and lime (CaO). Tests were
conducted with each of these chemicals on the wastewater
with the pH adjusted to 8.5, and 10 (see Figure I). A 15-liter
portion of the wastewater was treated in a manner similar to
the plant's treatment system except for the change in chemi-
cals and pH (and the flocculant changes noted above) so
that the plant could easily implement any recommended
changes. Individual waste streams were mixed in the proper
proportions. Appropriate retention times were allowed and
after flocculation and settling the supernatant (overflow)
was decanted and analyzed for its metal content. The
remaining sludge layer (underflow) was then drawn off and
filtered through a 0.45 micrometer filter. The filtrate was
analyzed for its metal content. Washed and unwashed
portions of the sludge cake were subjected to the EP and
ASTM-A extractions. Due to the small amounts of sludge
generated in some plants and to provide uniform results for
comparison the sludges were subjected to the EP and
ASTM-A extractions as follows.
A portion of the sludge cake (30 g) was washed by
homogenizing the sludge in 100 ml of deionized water and
mixing for 5 minutes. The washed sludge was then filtered
through a 0.45 micrometer filter. This filtrate (wash filtrate)
was analyzed for its metal content. This fraction reflected
the amount of the metal associated with interstitial water
which contributed to the leachability of the sludge. The
unwashed and washed sludge cakes were then extracted
identically by both the EP and ASTM-A extraction proce-
dures.
The EP was performed using 5.0 g of filter cake and the
ASTM-A extraction used 20.0 g of filter cake. The extracts
from these extractions were analyzed for metals.
Analytical results from these laboratory tests were
compared to each other and to the plant's samples to deter-
mine which combination of chemicals and pH resulted in
the best performance based on effluent quality and sludge
leaching characteristics.
Sludge Leachability
Leachability studies on washed and unwashed sludges
were performed using the EP and ASTM-A extraction pro-
cedures. These extractions differ considerably in that the
EP is conducted using an acidic (pH 5) extraction whereas
the ASTM-A procedure is an extraction with deionized
water.
The Cd, Zn and Cr levels in the ASTM-A extracts for
Plant 2 washed and unwashed sludges followed the same
trends as the washed filtrate and unwashed filtrate respec-
tively. Chromium was well stabilized against leaching having
values near or below its detection limit. The lowest leach-
ability of metals was observed with CaO and NaOH treat-
ment at pH 10. The lower levels of metal in the ASTM-A
extracts appeared to be mainly due to a dilution of the
interstitial water and not to additional leaching by the
ASTM-A extraction. The EP extracts show much higher
levels of leaching of these metals due to their increased solu-
bilities at pH 5. Cadmium and Zn levels were high for both
washed and unwashed sludges. They exhibited little vari-
ability with precipitation chemicals and showed minimal
pH effects. The washed sludges leached significantly lower
amounts of Cr. Unwashed samples showed a pH effect favor-
ing pH 8.5. Precipitation by Na2CO3 resulted in a 10-fold
increase in Cr leachability.
In Plant 3, Cd was readily leached in the EP extraction
while negligible leaching occured in the ASTM-A extrac-
tion. This contrasted with the behavior of Cr. The low leach-
ability of Cr in the EP extraction compared to the ASTM-A
extraction may result from the reduction of Cr6+, under the
acidic conditions of the EP extraction.
The most stable sludge generated in Plant 4 experiments
may be interpreted in terms of the leachability of Cu and Ni,
the two predominate metals in the waste stream. Chromium
leached less than 1.0 mg/1 in both the ASTM-A and EP
extractions. Lime at pH 10 produces the most favorable
levels of metals under the EP extraction. There was much
lower variability in these sludges under ASTM-A
extraction conditions.
In Plant 6, the EP extract of the CaO precipitated sludge
at pH 10 showed the lowest levels of Ni. The washed and
unwashed sludges extracted by ASTM-A leached very little
Ni. Chromium was best stabilized in CaO and NaOH
sludges precipitated at pH 10 for the EP extraction while
Table 4
Results of Flocculation Study
Optimum Concentration (mg/L)
Plant
Hocculating
agent
Blank
Separan AP-273
Magmfloc 836A
1.67OE
WT-3000
Separade P-3
Pe-col
Floe 306
Hercofloc
Manufacturer
Dow
Cyanamid
Calgon
Calgon
Benchmark
Allied Colloids
EPEC
Hercules
* Indicates flocculating agent and concentration
( ) Indicates approximate concentration used in
2
poor
poor
2.0*
poor
8.0
--
—
—
—
used for each
the plant.
3
poor
poor
poor
poor
0.5*
—
—
—
—
plants treatment
4
poor
1.0*
poor
poor
4.0
15(5)
—
—
—
study.
6 7
poor poor
40 1.3,;*
20
poor
poor
2 0*(6) —
(0.1)
8
poor
2.0*
poor
poor
40
50(5)
19
-------
or N
t
CENTRI-
FUGATIQN
a ..CO,
t
FILTER
LEAF
pH ADJUSTMENT
ADDITION
SETTLING
t 1
SLUDui:
111 —
L-
HOLD ONE
^^ MONTH
\
\
ASTM-A E
«" I pH B.5 or 10
— H 1
— »t
VACUUM " '*" INTERSTITIAL
FILTER fc WATER
\ 1
f 1 •
PA ASTM-A EPA
Fig. 1—Test Program and Analytical Plan.
pH 8.5 proved better for the ASTM-A extraction. The Cr
extracted by ASTM-A or the EP extractions was below 5
mg/l for all treatments and considerably better for some
treatments. It is interesting to note that the ASTM-A method
leached chromium as hexavalent chromium although little
or no Cr6+ was in the effluent or filtrates. It is unclear what
caused this result. The trends through the treatment series
for Cr(T) and Cr6* are very similar which tends to corrobo-
rate this result.
Plant 8 treatment with Na2CO3 produced a floe with very
poor settling characteristics. A significant amount of
particulate matter was apparent in the partially cleared
supernatant. This sludge cake also was very unstable
toward leaching of metals by both the ASTM-A and EP
extractions, especially at pH 10. Chromium and Cu levels in
the EP extract of Na2CO3 precipitated sludges were
exceptions and were by contrast the lowest for these metals
in the treatment series.
CONCLUSIONS
Effluent Quality
Plant 2
Cr concentration was reduced to below the analytical test
detection limit with NaOH and CaO3 at pH 10.
Cd and Zn were also lowered by NaOH, CaO and
Na2CO, at pH 10.
Plant 3
The presence of Cr+6 presented problems in all of the
simulation experiments. Cr+6 should have been chemically
reduced in the laboratory studies before the chemical
treatment.
The best Cd removal was achieved by CaO and NaOH at
pH 10.
Plant 4
N i, Cu and Cr were reduced by NaO H and CaO at p H 10.
Cr levels were below the analytical detection limit.
Plant 6
Cr and Ni were reduced below the analytical detection
limit by CaO and NaOH at pH 10.
Plant 8
No Cr*6 was found. Cr, Cu, and Ni were effectively
removed with NaOH, and CaO at pH 8.5, 10.
Sludge Leachab Hit \'
All plant sludges as initially tested by the EP test were
hazardous.
Plant 2
All treatments failed to produce a nonhazardous sludge.
CaO and NaOH at pH 10 produced nonhazardous leaches
of Cr.
Plant 3
The sludges failed the EP test for Cd. Cr remained
nonhazardous.
Plant 4, 6, 7
Made nonhazardous with all treatments.
Plant 8
No treatment conditions produced a nonhazardous
sludge.
RECOMMENDATIONS
The following recommendations are based on
observations made during the testing and engineering
evaluations of the data.
• To determine whether or not the conclusions
drawn from this test program are valid, it is
recommended that the electroplating shops from
this study adopt the optimum treatment chemical,
pH, and flocculant and study the results in their
effluent.
• Several more electroplating shops should have
their treated wastewater studied to see if the two
correlations generated from this study can, in fact,
predict ASTM-A results from the quantities of Cd
and Cr in the sludge filtrate.
• Owners and operators of electroplating shops
should be informed as to the results of this study so
that they may see that improvements can be made
to any electroplating shop. More educational
courses need to be given on wastewater chemistry,
treatment, and control.
This paper has been reviewed in accordance with the U.S.
Environmental Protection Agency's peer and administra-
tive review policies and approved for presentation and
publication.
20
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Outlook For New
Hazardous Waste Management Technology
Robert B. Pojasek, Ph.D.*
INTRODUCTION
In most cases, conforming to the proposed new effluent
regulations issued by the U.S. Environmental Protection
Agency (U.S. EPA) will bring about the production of more
heavy metal-containing sludges in the Metal Finishing
Industry. This comes at a time of strict regulation, also by
the EPA, of sludge disposal. Gone are the days of cheap
landfill disposal when $ 1.50 per ton was the going rate. Cost
today often pushes the $100 per ton mark.
It is highly likely that there will be fewer landfills in the
future and those which do exist will be tightly controlled. In
California, the Governor has announced an outright ban on
the disposal of "toxic metal" waste effective January, 1983.
In the meantime, disposal fees and enforcement will be
increased to promote early conformance to this ban. Other
states have also taken moves to severely limit the amount of
waste that is landfilled. The Ontario Waste Management
Corporation has gone on record signifying that only
"treated" wastes will be landfilled in the facilities it seeks to
develop.
Numerous publications and patents have appeared
describing technology effective for treating metal finishing
sludges and assorted other solids. At this time, very little of
this technology has gained wide acceptance for various
reasons, including inadequate promotion, limited
adaptability, and unfavorable economics. This paper will
examine some of the technological means that may be
utilized to handle the solid residuals from a metal finishing
plant. Special emphasis will be placed on those residuals
which are determined to be hazardous under the federal
Resource Conservation and Recovery Act (RCRA) or any
other set of state regulations.
Waste Minimization
The first line of defense is to minimize waste production
to the maximum extent possible. Many EPA publications
promote this concept with helpful suggestions. What the
metal finishing shop needs is an organized program to
consider and implement these plans.
A useful progam can be individually designed around the
following key steps:
• First, carry out a materials balance for water,
metals and other chemicals used in the operation;
• From the materials balance, reduce consumption
of water and chemical usage where this is indicated
and incorporate simple process modifications which
•Robert B. Pojasek, Ph.D.
Vice President
Roy F Weston, Inc.
111 South Bedford Street, Suite 206
Burlington, Massachusetts 01803
would enhance the potential for recovery of valuable
constituents;
• Segregate the process of effluents as far as possible
to facilitate the removal of metals; and
• Identify possible outlets for recovered materials and
provide any necessary process for producing the
wastes in an economically acceptable form (e.g.,
delisting treatment or simple volume reduction).
If this program is designed just for waste quantity
reduction a general approach to conduct the steps described
above is as follows:
• Identify all wastes;
• Prioritize all wastes according to costs;
• Develop waste quantity and/or elimination plans
for each waste;
• Assess the economic and technical feasibility of
these plans; and
• Implement those plans that are shown to be cost
effective.
It is often helpful to seek the assistance of a qualified
consultant. Independence from day-to-day operations and
familiarity with other successful operations can be most
useful to your staff in conducting your own program.
The American Electroplaters' Society, Inc. can assist its
member firms by keeping up-to-date on the activities of
various groups looking for means to help achieve waste
minimization. These groups include EPA's Hazardous
Waste Elimination Research Institute, United Nations' Pro-
gram for low-waste and non-waste technology, Ontario
Waste Management Corporation's Waste Reduction
Opportunities Study, and the California Office of Appro-
priate Technology's Alternative Waste Management Tech-
nologies Study, to name but a few. This information must be
made readily available and periodically updated.
In-Plant Waste Treatment
Many metal finishing plants are small operations. While
they can assist themselves by altering housekeeping practices
which will result in lower volumes of waste produced, it has
been argued that they cannot utilize in-plant technology
because of the relatively high capital costs of the equipment
and retrofitting. This may be true for some operations,
especially if recovery value or reduced disposal costs do not
significantly reduce the return on investment period.
Fortunately, this perceived lack of need has not completely
prevented the introduction of new technology applications.
Successful water use reduction programs have
dramatically altered the characteristics of the wastewater
streams. Low volume streams with higher metal
concentrations are more amenable to electrochemical
treatment. Because these units can be utilized close to the
process line, segregation of metals in the input stream is
possible, thus enhancing the prospects for metal recovery.
21
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Extended surface electrodes have been developed to
prevent fouling. The amount of waste streams requiring
treatment has been further reduced at some locations by
using advancing membrane technology to regenerate
process solutions until the impurity levels reach a point
where the above treatment is required.
There has been an increasing application of sodium
borohydride for chemical treatment of these waste streams
while enhancing the metal recovery potential of the product.
Perhaps other chemical treatment techniques can be
developed for this application. Finally, this waste stream can
be treated in a more or less classical metal precipitation
manner with dewatering. Metal recovery can be handled off-
site if the waste streams are not mixed prior to treatment.
Centralized Waste Treatment
The EPA has actively tested and promoted the concept of
centralized treatment of liquid metal finishing wastes. This
concept offers favorable economies-of-scale to the small
shop operations. There has been an increasing number of
these plants operating on a commercial basis. Because many
of them have located in industrialized areas and have
refrained from disposing any residues on-site, they have not
had the overwhelming difficulties in siting their facilities. A
number of companies in the business have received formal
exclusions (i.e., delistings) from EPA's RCRA regulations.
This enables them to handle plant residues as a non-
hazardous material. Those seeking to delist a material,
however, will have the burden of proof. If a waste is to be
delisted, it must be tested for each hazardous characteristic
that it was listed for and it must perform favorably on all the
tests. At least one operation which has obtained such an
exclusion plans to market the material as sanitary landfill
covering because of its relatively low permeability when
properly placed on the landfill.
Most of these centralized facilities are using classical and
chemical treatment processes (e.g., precipitation,
oxidation, reduction, dewatering, etc.) on mixed influent
streams. The EPA exclusions offer operating incentives by
dramatically lowering the residuals disposal costs. These
facilities should become the focus of research, development
and demonstration activities for improving recovery and
reuse opportunities. However, this is not happening. In
order to realize this opportunity, the facility would have to
encourage its customers to segregate waste streams. A
program to handle and treat these segregated streams must
be established and maintained.
When recovery of the waste stream is not being practiced
or when the residuals of the recovery operations are deemed
to be hazardous, solidification technology is sometimes
utilized to enable delisting. Many articles have been written
on the use of solidification. Some references are provided at
the conclusion of this paper. In spite of the articles, a great
number of "old wives tales" have been perpetuated—many
of them in EPA reports. The answers to some of these
falsehoods are as follows:
• There are over 40 commercially available processes
with many more generic processes being utilized;
• Some volume reduction systems are available to
actually reduce the bulk of the solidified waste;
• Some forms of strict encapsulation (especially with
thermo-plastics) are often more effective than
chemical fixation processes, especially for soluble
anions; and
• There are a number of processes to solidify organic
wastes with several quick-line processes leading the
way.
Reduction of secure landfill capacity should provi
incentives for increased use of solidification when delisti
and uses for the product can be found. However, a numt
of delistings in the metal finishing area have been obtain
without solidification. Increased recycling and ret
programs will also provide disincentives to the further use
solidification.
Waste Treatment Research and Development
It has been difficult to devote a lot of space in this article
describing new technologies for use in handling solid wasl
from the Metal Finishing Industry—there have been ve
few. EPA research and development budgets are bei
trimmed. The hazardous waste research and developme
institutes which have been established by EPA are n
considering metal finishing wastes as a priority item. EP
has spent technical assistance contract funds to assist stat
with concentrations of metal finishers in dealing with th
industry in its regulatory programs. However, these activiti
have not been well-coordinated and their reports have n
been well-distributed. The metal finishing industry h;
always been effective in working with the EPA Office t
Research and Development to develop new means <
wastewater treatment. It is time to dig in and complete tl
task by funding, to the extent needed, directed research an
development to maximize recovery potential of the soli
waste streams.
RELEVANT REFERENCES BY THE AUTHOR
"Developing Solutions to Hazardous Waste Problems.
Environmental Science and Technology, 14, 1980, p{
924-929.
New And Promising Ultimate Disposal Options, An
Arbor Science Publishers, Ann Arbor, Michigan, 1980.
Impact of Legislation and Implementation of Dispose
Management Practices, Ann Arbor Science Publishers
Ann Arbor, Michigan, 1980.
"Solid-Waste Disposal: Solidification," Chemica
Engineering,!^ August, 1979, p. 87.
"Novel Approach to Hazardous Waste Disposal in Nev
England," Journal of Northeast Pollution Contra
Association,13, 1989, pp. 36-46.
"Disposing of Hazardous Chemical Wastes,'
Environmental Science and Technology, 13, 1979, pp
810-814.
Stabilization / Solidification Processes for Hazardous
Waste Disposal, Ann Arbor Science Publishers, Anr
Arbor, Michigan, 1978.
Stabilization I Solidification Options for Hazardous
Waste Disposal, Ann Arbor Science Publishers, Anr
Arbor, Michigan, 1978.
"Stabilization/Solidification of Hazardous Wastes,"
Environmental Science and Technology, 12, 1978, pp.
382-386.
Using Solidification as a Waste Detoxification Process,
Ann Arbor Science Publishers, Ann Arbor, Michigan (in
preparation).
The work described in this paper was not funded by tht
U.S. Environmental Protection Agency and therefore tht
contents do not necessarily reflect the views of the Agency
and no official endorsement should be inferred.
22
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Segregated Neutralization for
Treatment of Concentrated Aluminum Finishing Wastes
F. Michael Saunders, Mesut Sezgin, Jesus M. Medero*
INTRODUCTION
Aluminum products are widely used in many industries
including construction, electrical, automotive, and food and
household good manufacturing industries. In the United
States approximately 6 * 106 Mg (metric tons) of aluminum
are used annually for domestic consumption.' Of the total
consumption, approximately 90% is converted to various
forms such as sheet, bar and wire, and subjected to a wide
variety of surface-treatment and finishing processes in well
over 600 major production facilities.2
With the emphasis of this study on water quality control, it
is appropriate to consider the nature of the finishing
processes used and the waste volumes produced in the
industry. In the aluminum finishing industry numerous
physical and chemical treatments (e.g., buffing, cleaning,
deoxidizing, painting and anodizing) are used to improve
surface appearance, durability, and adhesion properties.
Physical surface treatments conventionally utilized by the
industry include mechanical polishing, buffing and
brushing. The wastes associated - with these finishing
processes are solid wastes and oil-bound suspensions which
can be effectively recycled or treated and disposed. Chemical
finishing processes include chemical and electrochemical
etching and polishing, chemical milling, painting, and
anodizing. The wastewaters associated with these finishing
processes consist of large volumes of rinse waters, smaller
volumes of chemical spills, and spent or contaminated
finishing solutions and suspensions.
Wastewater Characteristics
Wastewaters from aluminum finishing processes contain
a variety of inorganic and organic contaminants resulting
from finishing solutions and aluminum products being
finished. These contaminants are discharged in rinse water
discharges and dragout and spills of finishing solutions.
They include aluminum, and other substances such as
arsenic, barium, cadmium, chromium, copper, iron,
manganese, magnesium, mercury, nickel, selenium, silver,
and silica.3 Spills of cleaning solutions and rinse waters
following cleaning contain sodium, carbonate forms,
phosphates, silicates, chelating agents and synthetic
detergents or soaps.4 In the etching step, which is utilized to
remove surface oxides, sub-surface detritus and grease, spent
etch wastes are generated which contain high levels of
aluminum, e.g., 10-75 g/L. In addition, spent etch solutions
may contain silicates, fluorides, nitrates, carbonates,
chromates, wetting agents, copper, zinc, and chromium.
Rinse waters following the etching step also contain these
*F. Michael Saunders, Associate Professor
Mesut, Postdoctoral Fellow
Jesus M. Medero, Graduate Research Engineer
School of Civil Engineering
Georgia Institute of Technology
Atlanta, GA
contaminants, but at lower concentrations. Desmutting
solutions are used in the removal of smudge films formed
during etching and are the primary solutions contributing to
effluent nitrogen in the form of nitrates.
In the anodizing step, a film of aluminum oxide is formed
on aluminum surfaces for decorative and protective
purposes using anodizing solutions composed primarily of
acids, such as sulfuric, chromic, phosphoric, and oxalic
acids. During anodizing, aluminum and other alloy metals
such as copper, zinc, arsenic, lead and iron are dissolved.
Aluminum concentrations in anodizing solutions may range
from 0.5-20 g/L. However, when aluninum concentrations
exceed prescribed limits, the anodizing solution is
regenerated using an ion-exchange resin or is discharged.
Regenerant acids and spent etch solutions are discharged to
a wastewater treatment system in the plant.
Coloring is applied on aluminum surfaces using organic
dyes, certain inorganic pigments, and electrolytically-
deposited metals.4 For this purpose, solutions containing
organic dyes, nickel, cobalt, tin, selenium, vanadium,
cadmium, copper, iron, magnesium, lead, chromium,
acetate, cyanide, and sulfite have been used. Sealing is
applied to modify the characteristics of the anodic coating. A
number of solutions have been used for sealing purposes
including distilled water with buffers, nickel acetate, salts of
aluminum, cobalt, zinc, copper, lead, chromium, and
sodium or potassium dichromate, alkali-metal silicates, and
waxes.
Water consumption rates in aluminum finishing plants
are in the range of 25 to 67 L/ kg of aluminum finished.5 High
water use rates are due to increased dragout of finishing
solutions which result in high rinse water requirements. In
addition, the formation of viscous liquid films on products
being finished requires large volumes of rinse water for their
removal.
Aluminum finishing wastewaters, therefore, contain high
levels of dissolved solids (e.g., 1.5-6.0 g/L for anodizing and
painting wastes, and up to 315 g/L for etch plant wastes)
which limit the reuse potential for these wastewaters. A
survey of aluminum finishing plants indicated that 0.9 to
2.4% of the mass of aluminum extruded and finished in
extrusion/anodizing plants was dissolved and discharged to
waste.6 Wastewaters also contain organic materials such as
detergents, etch sequestrants, spent dye, organic acids, and
acetate in the range of 30-100 mg TOC/L.6
Wastewater Treatment
Conventional treatment of aluminum finishing
wastewaters is achieved through mixing all rinse waters,
spent process solutions, and process spills in a multi-stage
neutralization system. Highly concentrated spent etch and
anodizing solutions are usually collected and stored for use
in controlling wastewater pH in the neutralization system.
Therefore, rinse waters and spills with relatively low levels of
dissolved aluminum are typically neutralized with highly
23
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10
O
O
C3
Z
O
Nl
10
I I
10-2 I
SETTLING ANALYSIS AT
POST-GENERATION TEMP., °C
48
80
72
O
D
A
10
SUSPENDED SOLIDS CONCENTRATION, G/L
100
Fig. 1—Effect of temperature on settling characteristics of sludges generated
at elevated temperatures and neutral pH.
o 10
O
z
I/I
Ul
O
10
,-2
T = 80°C
pH 7.0
pH 5.5
I III
1 10 100
SUSPENDED SOLIDS CONCENTRATION, G/L
Rg. 2—Effect of pH on settling characteristics of sludges generated at 80° C.
concentrated acidic and alkaline suspensions containing
high levels of waste aluminum. When combined waste-
waters are neutralized to pH values ranging from 6 to 8,
aluminum is precipitated as an aluminum hydroxide.
Wastewaters from painting processes utilizing chromate
1.0
10 20 30 40
SUSPENDED SOLIDS CONCENTRATION, G/L
Fig. 3—Batch flux curves for sludges generated by conventional ar
segregated (high temperature) neutralization of aluminum finishing waste;
solutions are generally pretreated for chromate reductioi
Hexavalent chrome is reduced to trivalent chrome, wil
reducing agents such as ferrous iron, sulfur dioxide or sulfit
and precipitated as a hydroxide at alkaline pH values.7
Neutralized anodizing and painting wastewaters a
typically polymer-conditioned and gravity settled. Clarifie
wastewater is either discharged to a receiving water <
sewerage system for additional treatment. Thickened sludgi
are either discharged to sludge lagoons for further thickenir
and consolidation or conditioned, dewatered, and dispose
of on land.
The results of a survey conducted on aluminum finishir
plants indicated that clarifier underflow suspensions had a
average suspended solids concentration of 22 g/L with
range of 0.1 to 50 g/L.6 With the use of mechanic
dewatering systems, sludge concentration was furthi
increased to a range of 1-20% with an average value <
16.5%. If it is assumed that the sludge solids contained on
aluminum hydroxide (A 1 (OH)3), the average survey value <
16.5% represented 17.5 kg of wet sludge for each kg <
aluminum precipitated. It was further reported that 0.8 t
2.4% of finished aluminum is dissolved during finishing.6 Th
would correspond to the production of 0.16 to 0.42 kg wi
sludge (at 16.5% solids) for each kg of aluminum finished.
a sludge solids concentration lower than 16.5%
encountered, the relative quantity of dewatered sludge f(
disposal would approach finished aluminum productio
levels.
To reduce the volume of sludge handled, other treatmei
techniques have been investigated. One of these treatmei
methods involves the segregation of spent finishing solutio
from dilute waste solutions (such as rinse waters) an
neutralization in a separate reactor. By this treatmei
alternative, sludge could be concentrated to 20% solid
instead of 2% solids as observed with conventional treatmei
24
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Table
1
Characteristics of Acidic Anodize and Caustic Etch Suspensions
Parameter
PH
Temperature, °C
Aluminum, g Ai* I.
Alkalinity, g 1. as CaCOi
Acidity, g/Las CaCO!
Color
Spent Anodtze
Suspension
055 13.5
21 50
750 51.0
405
340 —
2
1 3.5
50
45.8
454
—
Spent Etch Suspension
Sample No.
3
13.7
50
38.2
489
—
4
13.3
50
35.6
454
—
5
13.8
50
41.3
528
—
Sludge Generation
Sludge Generation
Hydraulic
Retention
X
ss
Run
1
2
3
4
5
indicates that
= Suspendec
pH
8.5
70
55
10.0
85
Time
(min)
10.2
9.2
92
10.2
10.2
the parameter was vanec
Solids
Table 2
and Dewatering Analysis Conditions For the Five Experimental Runs
Dewatering Test Variables
Specific Resistance Test Filter Yield Test CST Test
Form
Temperature Vacuum
X X
X
X
X
-
SS
X
x
x
x
x
Temperature
X
.
.
-
-
Vacuum
X
X
X
X
-
to determine effects on dewatenng properties of sludge while all the
SS Time
X
X
X
X
X
other parameters
-
X
X
X
X
Temperature
X
-
-
-
-
SS
X
X
X
X
X
were kept constant.
Table 4
Impact of a Segregated Treatment of Spent Process Wastewaters at
Sludge Plant A"3 on Slud9e Dewatering Characteristics
Sludge Generation Specific Resistance
Generation Temperature R(10lom/kg) Filter Yield, F(kg/m2 s * 103) CST (s)
pH °C FSS' R FSS F Cake Solids, % FSS CST
Segregated Neutralization
5.5 80
7.0 80
8 5- 80
10.0 80
Conventional Neuralization
70' 25
'Feed suspended soltds concentration.
filter yield data from run #5
'Conventional sludges from Plant A-.1
12.8-
16.4-
208-
25.4-
3.4-
g'l
1575
151.1
157.8
256.3
36.1
22.5-
2.33-
1.33-
0.34 -
28-
31.0
3.18
2.95
0.87
38
35.0
35.0
35.0
35.0
3.4-36.1
2.8
9.6
6.2
0.78
0.70 - 5.71
34.0
34.6
42.2
52.8
8.5 - 9.2
35.0
35.0
35.0
35.0
3.4 - 36. 1
63.0
25.0
25.0
25.0
18.1 - 53.7
Table 5
Impact of a Segregated Treatment of Spent Process Wastewaters at
Plant A-3 on Required Vacuum Rlter Area and Mass of Sludge for Disposal K
Generation
pH
5.5
7.0
85
100
70
Generation
Temperature
°C
80
80
80
80
25
Feed Suspended
Solids
Concentration
Kit
150
150
150
150
-
Filter
Yield
kg/m2-s
l.IOX I0:
4.00 x 10"'
3.40 X 10"
6.00 X 10"'
5.71 X 10"'
Cake Solids
Concentration
%
34.2
34.8
40.0
46.7
9.2
Filler Area
Required
m2
11.41
3.14
3.69
20.91
21.97
Mass of Sludge
for Disposal
kg/day
7,924
7,787
6,775
5,803
29,457
25
-------
pH METER/CONTROLLER
ACID ANODIZE
WASTE RESERVOIR
ALKALINE ETCH
WASTE RESERVOIR
AUTOMATIC
TEMPERATURE
CONTROLLER
REACTION VESSEL
Fig. 4—Schematic diagram of laboratory-scale neutralization systems.
IO10
-pH85IRUN=5)
_L_
_1_
_1_
50 100 150 200 250
, SUSPENDED SOLIDS CONCENTRATION, g/l
Rg. 5—Variation of specific resistance with suspended solids concentration at
room temperature for sludges generated at 80° C and at various pH values.
O
cc
CO
o
400
200
100
80
60
40
20
10
ITT
pH5.5
pH8.5 (RUN #5)
I
I
I
I
0 50 100 150 200 250 300
SUSPENDED SOLIDS CONCENTRATION, g/l
Rg. 6—Variation of capillary suction time (CST) with'suspended solids
concentration at room temperature for sludges generated at 80° C and at
various pH values.
technologies.8 Ledfore9 reviewed solid-liquid separations in
the treatment of metal finishing wastes and indicated that
the neutralization of concentrated acidic wastes was shown
to result in improved handling and filterability when
neutralized or aged at 71-82°C. The sludge moisture content
following dewatering was also significantly reduced.
Furthermore, pH adjustment of the neutralized liquor was
found to affect the settling rate of sludges.
An industrial survey conducted by Ramirez10 indicated
that 80 to 85% of the mass of wastewater aluminum at an
anodizing plant was contained in concentrated spent etch
and anodizing wastewaters.6 Therefore, segregated
neutralization of these wastes would reduce the solids
loading on a conventional treatment system. More
importantly, depending upon pH and temperature of
neutralization, a sludge with much improved settling and
dewatering characteristics would be produced, resulting in
major reductions in the volume of wet sludge to be disposed.
The objective of the study reported herein was to evaluate
the effect of neutralization pH of concentrated etch and
anodization wastes on dewatering characteristics of sludge
generated at 80° C. Other objectives included determination
of the effects of sludge viscosity, suspended solids
concentration, form time and applied vacuum on the
dewatering and handling characteristics of the sludges
formed.
EXPERIMENTAL METHODS AND MATERIALS
Etch and anodize wastewater samples from an aluminum
finishing industry were collected and mixed in a continuous
flow bench-scale neutralization system. Aluminum
hydroxide suspensions generated at various pH values were
examined for their dewatering properties under various
experimental conditions including temperature, vacuum
and form time.
The continuous flow neutralization system consisted of a
0.8-L reaction vessel stirred at 150 rpm with a single-paddle
metal stirrer as presented in Figure 4. The contents of the
reaction vessel were maintained at a constant temperature of
80° C with an automatic temperature controller which
provided recirculation of the hot/cold distilled water
through an external water jacket.
Peristaltic pumps equipped with flow rate controllers were
used to pump etch and anodize wastes to the reaction vessel.
During sludge generation, the anodize waste flow was kept
constant while the etch waste flow was regulated with an
automatic pH controller to maintain the pH of a neutralized
suspension at required values. Influent flow rates were
26
-------
50 100 150 200 250 300
SUSPENDED SOLIDS CONCENTRATION, g/l
Fig. 7—Variation of filter yield with suspended solids concentration at room
temperature for sludges generated at 80° C and at various pH values.
adjusted to maintain hydraulic retention times of
approximately 10 minutes in all runs. Neutralized aluminum
hydroxide suspensions were removed from the reactor by
vacuum and transferred to a glass container held at the
temperature of generation in a constant temperature water
bath.
Sulfuric acid anodize and caustic etch suspensions were
obtained from a major regional aluminum finishing plant.
The characteristics of these wastes are indicated in Table 1.
Since changes in waste characteristics after prolonged
storage were observed with spent etch suspensions, fresh etch
samples were used for each experimental run. For this
reason, Table 1 contains data for five spent etch samples
used during the study. Measurements of pH, temperature,
alkalinity and acidity were made in accordance to the
methods described in Standard Methods for the
Examination of Water and Wastewater.12
Dewatering tests were conducted with aluminum
hydroxide suspensions using a Buchner funnel, and filter leaf
and Capillary Suction Time (CST) apparati. Prior to
dewatering tests, aluminum hydroxide sludges collected in a
20-L glass container were allowed to settle and a series of
dilutions in the range of 10 to 100% volume of the settled
sludge were prepared using clarified supernatant liquid.
Sludge specific resistance values were measured to
evaluate sludge dewatering ability.13 Filtration temperature,
and vacuum and feed suspended solids concentrations were
varied to determine the effect of these parameters on
dewaterability of sludges generated at different pH values.
Filter leaf test measurements were used to determine filter
yields in accordance with the method described by
O'Connor.10-13 Similarly, the effects of filtration temperature
and vacuum, feed suspended solids concentration and form
time on filter yield were evaluated. CST measurements were
conducted using a type 92 /1 CST appartus and a hollow,
cylindrical, metal reservoir of 10 mm diameter. The effects of
50 100 150 200 250 300
SUSPEMDED SOLIDS CONCENTRATION, g/l
Fig. 8—Effect of feed suspended solids concentration on cake solids
concentration at room temperature for sludges generated at 80° C and at
various pH values.
45
30
^— pH10
pH85(RUNst5)
pH85(RUN«1)
pH7 0
pH55
GENERATION TEMP = 80 C
ANALYSIS TEMP = 25'C
VACUUM = 38cm Hg
1 I
0 50 100 150 200 250
SUSPENDED SOLIDS CONCENTRATION, g/l
300
Fig. 9—Variation of cake solids concentration with suspended solids
concentration at various pH levels in specific resistance tests.
temperature and suspended solids concentration on
dewaterability of sludges were determined.
To investigate the effect of neutralization temperature and
pH on settling characteristics of sludges produced by
segregated neutralization, extensive studies were conducted
by Saunders et. al." Waste etch suspensions (i.e., 5.5N
NaOH at 2.4 M Al) and anodize suspensions (8N H2SO4 at
0.6 M Al) were neutralized at pH values ranging from 5.5 to
8 and temperatures from 65 to 90° C. As indicated in Figure
1, temperature variations of 48 to 72° C (for suspensions
generated at temperatures of 65 to 90°C and a pH of 7) did
not significantly affect zone settling properties. However,
sludge suspensions generated and analyzed at 80° C
indicated marked improvement in sludge thickening
characteristics with increasing pH values, as indicated in
Figure 2. A comparison of batch flux settling data, for a
suspension generated at pH 7 and 80° C using segregated
neutralization with a conventional suspension generated at
neutral pH values and ambient temperatures, indicated that
27
-------
10L
5x10"
SUSP. SOLIDS CONC. (g/ll
U
z
CC
o
2x10"
10"
So
I I I I
104
2x104
5x104
10b
APPLIED VACUUM, N/m2
65
50
RUN --
FEEDSUS SOLIDS
CONC , g/l
30
Rg 10—Evaluation of compressibility coefficient, &,, at various suspended
solids concentrations for suspension generated at a pH of 5.5 and a
temperature of 80° In experimental run 3.
- pH
I
1(T3
FEEDSUS SOLIDS
CONC , g/l
8 10 20 40
APPLIED VACUUM, cm Hg
60
80 100
Rg. 11—Variation of filter yield with form vacuum for sludges generated at
different pH levels.
an approximate 3-fold reduction in sludge volume could be
achieved at a solids flux loading of 1 kg/ m2-h, as shown in
Figure 3. Segregated neutralization therefore resulted in the
APPLIED VACUUM, cm Hg
Rg. 12—Effect of applied vacuum pressure on cake solids concentration .
room temperature for sludges generated at 80 C and at various pH values
production of a suspension which thickened much betti
than those generated using conventional neutralization.
RESULTS AND DISCUSSION
Five experiments were performed to determine the effei
of neutralization pH on the dewatering characteristics (
aluminum hydroxide sludges generated at 80° C. For eac
run, or neutralization pH, the dewatering properties of tt
sludges were measured under a variety of test conditions i
given in Table 2.
Sludge Dewaterability at Various pH Values
The relationships between specific resistance an
suspended solids concentration at various pH levels ai
presented in Figure 5. Because of random variations i
specific resistance with suspended solids concentratioi
specific resistance did not appear to be affected by suspends
solids concentration. There was a strong indication th;
specific resistance decreased with increasing pH values. Fc
example, at pH 5.5, the specific resistance wj
approximately 2.50 x 10" m/kg. When the pH was increase
to 7.0 and 8.5, the specific resistance decreased to 2.7 x 10
and 2.0 x 10'° m/kg, respectively. A further increase in pH t
10 resulted in a decrease in specific resistance to an averaj
value of 5.1 x 109 m/kg. A second experiment for a sludg
generated at pH 8.5 (Run #5) also resulted in a specifi
resistance of 5.1 x 109 m/kg. This may be attributed t
several reasons. At this low level (=» 5 X 109 m/kg) it
extremely difficult to measure specific resistance due to rapi
dewatering rates. More importantly, fresh etch waste w£
collected each time an experiment was conducted and th
may have contributed to the formation of sludges wit
differing properties. Nevertheless, the effect of pH on specif
resistance followed a pattern similar to that observed b
Ramirez10 for settling properties.
Variations in CST with suspended solids concentratio
and at various pH values are shown in Figure 6. CST valu<
were observed to increase with suspended solic
28
-------
•3,
>
cc
1 fl-
032
-6**
RUNw
pH
FEEDSUS SOLIDS
CONC., g/l
7.0
5.5
10.0
8.5
151.1 O
157.5 D
1844 A
159.6 •
I
I
10
20 40 60 80 100
TIME OF CAKE FORMATION, s
Rg. 13—Filter yield vs time of cake formation.
concentration and decrease with increasing pH. As observed
with specific resistance data at pH 8.5 (Runs #5 and #1),
lower CST values also were observed at pH 8.5 (Run #1).
However, both runs resulted in similar CST values per unit
weight of solids.
The relationships between filter yield and feed suspended
solids at various pH levels are presented in Figure 7. No
relationship is given for the sludge in Run #1 because the
filter yield was determined at a vacuum of 51 cm of Hg
instead of 38 cm of Hg used at other runs. It is apparent that
an increase in pH from 5.5 to 7 resulted in an increase in filter
yield. As indicated previously, specific resistance and CST of
these sludges were both observed to decrease with sludge
generation pH, indicating sludge filtrability was improved
by increasing generation pH. From these observations, it
would be predicted that filter yield should have increased
with increasing pH. However, this was not the case with the
results presented in Figure 7. Filter yield generally increased
with increasing pH except for the sample generated at pH 10,
which was contrary to indications from CST and specific
resistance data. Variations in filter media used for filter leaf
and specific resistance measurements were shown to have no
effect on the dewatering trends. Factors affecting pickup of
sludge particles in the up-flow filter leaf test, as opposed to
development of a sludge cake with down-flow in the specific
resistance test, were considered to have major impact on the
variation from the trend of improving dewaterability with
pH.
<
CC
O
O
Q
_J
S
60
55
50
45
40
35
30
RUN#
2
3
4
5
pH
7.0
55
10.0
8.5
SUSP. SOLIDS CONC (g/l)
151.1
157.5
184.4
159.6
A
O
D
20
40
60
80
100
TIME OF CAKE FORMATION, s
Rg. 14—Effect of time of cake formation on cake solids concentration at room
temperature for sludges generated at 80 C and at various pH values
In Figure 8, the effect of feed suspended solids
concentration on cake solids concentration at various pH
levels is presented for the filter leaf tests. For sludges
generated at pH 5.5 and 7.0, cake solids concentrations are
relatively constant with average values of 33.8% and 34.6%,
respectively. Whereas, cake solids concentrations decreased
with increasing suspended solids for the sludges generated at
pH 8.5 and 10. This indicated that at the onset of the
filtration process, particles picked up on the surface of the fil-
ter leaf formed a layer of low porosity. This layer lowered the
passage of liquid coming out from the subsequent layer
simultaneously formed in the course of filtration. Because of
the higher resistance exerted by the first layer, the pressure at
the interface of this layer and liquid was greatly reduced.
Therefore, because of the lower pressure at the surface the
next layers would be thin (e.g., lower filter yields) and have
higher moisture content, as shown in Figure 8 with sludges
generated at pH 8.5 to 10. However, in specific resistance
experiments, cake solids concentrations were fairly constant
with increasing suspended solids concentration at all pH
levels (Figure 9). This observation was an indication of the
gradual decrease of pressure through the cake rather than a
sharp decrease in the first layers of the sludge in the filter leaf
test experiment. The possible explanation of variations in
behavior of the sludge in these two tests may be that there
was preferential pick-up of small-sized particles in the filter
leaf test experiments, whereas this did not occur for specific
resistance experiments. The implication of these findings is
that since the filter leaf test closely approximated the
conditions present in vacuum filtration of sludges,
predictions made about filter yields of vacuum filters based
on the specific resistance experiments may not be accurate,
especially for sludges in the low specific resistance values.
29
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Vacuum Effects on Dewaterability
The effect of applied vacuum on specific resistance of
sludges was examined at various levels. A typical
relationship between specific resistance and vacuum
pressure at various suspended solids concentrations is
presented in Figure 10. When plotted on logarithmic
coordinates, the relationship can be expressed by a linear
relationship and be presented by the following expression:
(1)
in which r = specific resistance; r' — cake constant; P —
applied vacuum; and SH — compressibility constant. The
compressibility constant, s,,, was determined from the slope
of the linear relationship and indicates the relative
compressibility of a sludge. When s,, is zero, the sludge is
incompressible and increasing values of s,, indicate increasing
compressibility of a sludge. As apparent from the results,
suspended solids concentration did not affect the
compressibility constant for the sludges. Therefore average
values of the compressibility constant were assumed to be
representative for each sludge. Average values of the
constants for various pH levels are presented in Table 3. The
compressibility of sludges decreased with increasing pH
which was consistent with the results of specific resistance
experiments.
Variation of filter yield with applied vacuum for sludges
generated at various pH levels is presented in Figure 11.
When plotted on a logarithmic scale, the relationships
followed a linear relationship which was consistent with the
theoretical yield expression:
Y =
[2Pwk T
^ J
(2)
in which Y = filter yield; P = applied vacuum; w = dry solids
deposited per unit volume of filtrate; k = form time fraction;
yu = viscosity; r = specific resistance; and ft = total cycle time.
In equation 2, k, /u and ft are constants when only applied
vacuum is varied. In addition, w may be assumed to be
constant and r varies with applied vacuum when the cake is
compressible. Therefore, equation 2 may be combined with
equation 1 as follows:
Y = A p d-So)/2
where A =
[2wk 1
MrU J
(3)
A logarithmic plot of equation 3 results in a linear
relationship with a slope of (l-s)/2. From Figure 11, as pH
increased, the slope of the curves increased indicating that
the compressibility constants decreased, which supported
the previous observation that compressibility constants
decreased with increasing pH levels. Furthermore, at a
similar feed suspended solids concentration an increase in
pH from 5.5 to 7 yielded an increase in filter yield. Further
increase in pH to 10 resulted in lower filter values even
though higher feed suspended solids concentrations were
utilized.
Variations of cake solids concentration with applied
vacuum are presented in Figure'12. For each sludge, cake
solids concentration was observed to increase linearly with
applied vacuum. Since cake solids concentration is an
indication of the sludge volume which must be disposed of,
the benefit of increasing applied vacuum to increase cake
solids concentration should be weighed against the increa
in capital and operational costs for dewatering, i.e., decrea
filter yields.
Effect of Time of Cake Formation on Filter Yield
The variation of filter yield with the time of c;
formation is presented in Figure 13. The data were collec
at constant feed suspended solids (FSS) concentrations
various generation-pH levels. The slopes of the linear pi
ranged from 0.26 to 0.43 which indicated that filter medii
resistance was not significant and was consistent with 1
previous conclusion of the presence of insignificant fil
medium resistance.
At any cake formation time, filter yield was observed
increase and subsequently decrease with increasing pH.
similar pattern with regard to the effect of pH on filter yi<
was observed with numerous feed suspended sol
concentrations as shown in Figure 7
Relationships between cake solids concentration and t
time of cake formation are presented in Figure 14. While t
sludges generated at pH 5.5 to 7.0 exhibited constant soli
concentration with varying time of cake formation, the ca
solids concentration for the sludges generated at pH 8.5 to
decreased. As previously discussed, initial sludge layers m
have formed an impervious cake with fast-filtering slud£
thereby lowering the filtration rate of subsequent layers ai
resulting in decreasing cake solids concentration as t
number of layers increased.
ENGINEERING IMPLICATIONS OF SEGREGATEC
NEUTRALIZATION
To assess the impact of the segregated neutralization
spent etch and anodize wastewaters on dewaterii
characteristics of sludges in the aluminum finishing industr
data in Table 4 are presented. The data include specif
resistance, filter yield and CST results for both segregate
and conventional neutralization. The sludges generated I
segregated neutralization could be concentrated by gravi
sedimentation to a suspended solids concentration of 256
g; L whereas the sludge generated with the convention
technique could be concentrated to 36.1 g/L, only afti
much longer settling periods were used. Since filter yield an
CST both varied with suspended solids concentration, i
order to make a comparison between segregated an
conventional neutralization, it was necessary to normalii
filter yield and CST values to a fixed suspended solic
concentration. Therefore, a suspended solids concentratio
of 35 g/ L was arbitrarily selected for the compariso
purposes.
As apparent from Table 4, specific resistance values at
pH of 7 and temperature of 80° C ranged from 2.3 X 10101
3.2X 10'° m/kg and were about 10 times lower than those fo
conventional neutralization (i.e., 2.8 X 10" to 3.8 X 101
m/kg). Similarly, the filter yield value doubled to 9.6 X 10
kg/m2-s from 5.71 X 10 3 kg/m2-s and CST was halved to 25
Table 3
Effect of Generation pH on Compressibility Constar
Generation
pH
5.5
7.0
10.0
Compressibility Constant
0.48
044
0.34
30
-------
from 53.7s with the application of segregated neutralization.
More importantly, cake solids concentration, which is an
indicator of manageability of a sludge for ultimate disposal,
was increased to about 35% from 9%. In addition, with
proper selection of neutralization pH (pH >7), cake solids
concentration may be further increased and specific
resistance may be reduced.
To further illustrate the impact of segregated treatment on
sludge disposal problems encountered with conventional
treatment, vacuum filter surface areas required to dewater
each of the sludges in Table 4 are presented in Table 5. In
addition, the total mass of wet sludge produced after
dewatering is presented. The data were based on an assumed
total mass flow of 938 kg/day of aluminum which was
determined to be the mass flow of aluminum in spent etch
and anodize wastewaters in an industrial plant. ° It was
assumed that, upon neutralization, all aluminum was
precipitated as Al (OH)s and concentrated to 150 g/L by
gravity sedimentation for segregated neutralization. The
selection of the suspended solids concentration of the
thickened sludge was based on the fact that all the sludges
generated in this study were observed to settle to a
concentration of 15% solids. Also, a 6-h shift of vacuum filter
operation was assumed for sludge dewatering in these
calculations.
The data presented in Table 5 clearly demonstrate that
much lower filter areas and sludge volumes Were obtained
with the application of segregated treatment. At a pH of 7, a
filter area of 3.14 m is required for segregated neutralization
as opposed to 22 m2 required for sludges neutralized
conventionally. Similarly, segregated treatment resulted in a
sludge mass of 7,787 kg/d while conventional treatment
produced 29,457 kg/d of sludge solids.
In summary, by the use of the segregated treatment
technique, not only can significant reductions be achieved in
the area of vacuum filters, but also a decrease in the sludge
quantity and an improvement in sludge handling
characteristics can be obtained.
CONCLUSIONS
The following conclusions can be drawn from this study:
1. Neutralization pH has a dramatic effect on the
dewatering properties of sludges generated at 80° C using
concentrated aluminum finishing wastewaters. Specific
resistance and CST values of sludges decreased with
increases in pH from 5.5 to 10. However, filter yield first
increased in the pH range of 5.5 to 7.0 and then decreased
with further increase in pH to 10. It was hypothesized that
the decrease in filter yield at high pH levels was due to
increased cake resistance which was not observed with the
specific resistance test. Cake solids concentrations in filter
leaf test experiments were higher at alkaline pH levels than at
neutral or acidic pH levels.
2. No influence of feed suspended solids concentration on
specific resistance was observed. However, CST and filter
yield both increased exponentially with feed suspended
solids concentration. Cake solids concentrations determined
from the filter leafiest experiments were not affected by feed
suspended solids concentration at pH levels of 5.5 to 7.0.
However, they decreased with increases in the feed
suspended solids concentration at pH levels of 8.5 to 10.
3. The relationship between specific resistance and
vacuum pressure can be expressed by r = r1 P80 at any
generation pH level. The compressability constant, sb
decreased with increasing pH levels and thus indicated the
sludges were relatively incompressible.
4. Filter yield increased exponentially with an increase in
form vacuum. The observation that the compressibility
constant decreased with increasing pH levels was also
supported by the relationship between filter yield and form
vacuum. Cake solids concentration increased linearly with
the increase in form vacuum.
5. Filter yield increased with the increase in time of cake
formation. However, cake solids concentration was
independent of time of cake formation at pH levels of 5.5
and 7.0 and decreased at when the pH was in the range of 8.5
to 10.
6. Dewatering properties of aluminum hydroxide sludges
generated by segregated neutralization were significantly
better than those of sludges generated by the conventional
method at aluminum finishing plants. A decrease of 86% in
vacuum filter area, and a significant decrease in the amount
of wet sludge for disposal, were observed when the sludge
generated at pH 7.0 and 80° C was compared with the sludge
generated at pH 7.0 and room temperature with the use of
conventional neutralization.
7. Aluminum finishing industries can substantially
improve dewatering and handling characteristics of their
sludges by the application of a segregated treatment system
of spent concentrated etch and anodize wastes at high
temperatures.
REFERENCES
1. American Bureau of Metal Statistics Inc., Non-Ferrous
Metal Data 1978, ABMS, New York (1979).
2. Aluminum Statistical Review 1977, The Aluminum
Association, Inc., Washington, D.C. (1978).
3. Wernick, S., and Pinner, R., The Surface Treatment
and Finishing of Aluminum and its Alloys, 4th edition,
vol. 2, Robert Draper LTD, Teddington (1972).
4. Lowenheim, A. F., Electroplating, McGraw-Hill Book
Corp., New York (1978).
5. Steward, F. A., and McDonald, D. C., "Effluent
Treatment from Aluminum Finishing Processes,"
Proc. 66th American Electroplateds Society Technical
Conference, Atlanta, Georgia (1979).
6. Saunders, F. M., and Sezgin, M., "Characterization,
Reclamation and Final Disposal Techniques for
Aluminum-Bearing Sludges". Final Report submitted
to the Aluminum Assoc. Inc., Washington, D. C,
Report No. SCEGIT-82-108.
7. Ceresa, M., and Lancy, L. E., "Metal Finishing Waste
Disposal-Part III", Metal Finishing, 66, 6, 112-118
(1968).
8. Waste Treatment, Upgrading Metal Finishing Facili-
ties to Reduce Pollution, U.S. Environmental
Protection Agency, Technology Transfer (1980).
9. Ledford, R. F., "Solids-Liquid Separation in the
Treatment of Metal Finishing Wastes", Plating, 42,
1030- 1036(1955).
10. Ramirez, R., "Effect of Precipitation Temperature on
Settling Properties of Aluminum Finishing Sludges,"
Special Research Problem Report, School of Civil
Engineering, Georgia Institute of Technology, Atlanta,
Georgia (1979).
11. Saunders, F. M., Sezgin, M., and Ramirez, R. R.,
"High Temperature Treatment of Concentrated
Aluminum Finishing Wastes". Proc. 67th Annual
American Electroplater's Society Technical
Conference, Environ. Session, Milwaukee, Wisconsin,
31
-------
(1980). Professors, (1975).
12. Standard Methods for the Examination of Water and
Wastewater, 14th Ed., New York, American Public
Health Association (1976). This paper has been reviewed in accordance with the U.S.
13. O'Connor, J. T., Ed., Environmental Engineering Unit Environmental Protection Agency's peer and administra-
Operations and Unit Processes Laboratory Manual, tive review policies and approved for presentation and
2nd Ed., Association of Environmental Engineering publication.
32
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Hazardous Waste Treatment Facility Siting
Methods, Concerns and Progress?
Steven I. Taub*
ABSTRACT
The process of locating an area in which to construct a facility meeting att the relevant
RCRA criteria for the treatment and disposition of potentially toxic and hazardous wastes
is difficult, expensive, time consuming and extremely risky. This statement may evoke
much controversy, but the inescapable conclusion that over the last several years it has been
virtually impossible to implement the RCRA rules through the construction of new and
needed processing facilities, is a fact that we must att, unfortunately, Bve with. At times it
appears almost as if the RCRA rules, passed with att of the best possible intention, are
nothing more than a roadblock to the development and use of new, innovative and much
needed waste treatment technologies.
Stablex Corporation has firsthand experience in attempting to site plants utilizing such
innovative techniques, and has indeed achieved a degree of recognition in that it has been
granted a temporary interim delisting from the USEPA for 29 categories of potentially
toxic and hazardous wastes. Stablex has even obtained permits for the construction of these
facilities, but after more than four years of development and the expenditure of millions of
dollars, still has not begun commercial operation. A plant permit sought in the Province of
Quebec, Canada, however, has been granted, with construction underway as of October 1,
1981, after a process of only a little more than one year.
The reasons for the difficult siting environment shall be discussed from a firsthand
viewpoint and specific proposals made to help augment the construction of the needed
facilities.
CONCLUSION
In this paper I will introduce to you what we believe to
be the origin of the problem of industrial toxic and
hazardous waste disposition. I will explain something about
Stablex Corporation, its development and its business. I will
tell you about how we have gone about attempting to
implement our business, which in effect was created as a
result of the passage of the RCRA Act. I will review for you
our long and arduous siting process in Groveland, Michigan
which resulted in long litigation and is still unresolved even
after four years of bitter debate and millions of dollars
having been spent. I will cite the innovative approach that
Stablex Corporation and the Gulf Coast Waste Disposal
Authority took to place a regional treatment center into
operation and the bitter opposition that emerged by not only
well-meaning state citizens, but also by competitors who had
a significant economic stake at risk. I will briefly discuss how
reports that are written by well-meaning state officials can
amplify certain facts and leave out others and be accepted as
the total truth rather than as an edited version of the truth. I
will discuss how the support of high-ranking state officials,
for example the Governor of the State of Virginia, can lead
to disappointment and no progress.
*Steven I. Taub
Stablex Corporation
Two Radnor Corporate Center
Radnor, Pennsylvania 19087
Stablex believes it can provide a part of the solution. We
have never said that we are the entire solution, nor do we
pretend that we will ever be. If Stablex had ten times the
capital resources presently available to it it still could not
provide all of the services needed to adequately treat and
place the materials previously discussed. Therefore, we seek
a start. We have made the offer that we will build a plant
anywhere there is a reasonable market, at our own expense,
to demonstrate that we can do exactly what we say. We
make the offer again. We ask for assistance from community
leaders and industrialists who recognize that now is the time
to act to solve this most pressing of problems, the adequate
disposition in an environmentally acceptable fashion of
potentially toxic and hazardous wastes generated by
industries serving all Americans and which industries allow
us to enjoy the standard of living we currently have.
INTRODUCTION
The process of locating an area in which to construct a
facility meeting all relevant RCRA criteria for the treatment
and disposition of potentially toxic and hazardous wastes is
difficult, expensive, time consuming and extremely risky.
This statement may evoke much controversy, but the
inescapable conclusion that over the last several years it has
been virtually impossible to implement the RCRA rules
through the construction of new and needed processing
facilities, is a fact that we must all, unfortunately, live with.
At times it appears almost as if the RCRA rules, passed with
33
-------
all of the best possible intentions, are nothing more than a
roadblock to the development and use of new, innovative
and much needed waste treatment technologies.
The RCRA Act was passed by Congress in 1976. The
specific purpose of the law was to "provide technical and
financial assistance for the development of management
plans and facilities for the recovery of energy and other
resources from discarded materials and for the safe disposal
of discarded materials, and to regulate the management of
hazardous waste." Clearly, a major intent of Congress was
to ensure that all citizens of the United States of America be
protected from potential adverse environmental impacts as a
result of improperly managed and poorly handled waste
disposition facilities. Congress further attempted by this
landmark law to make practical by technological innovation
new and environmentally compatible techniques to treat and
detoxify and/or destroy the bulk of potentially toxic and
hazardous wastes. Congress reasoned that if the old and
environmentally unsound techniques and processes then in
existence, many of which are still in existence, could be made
either unlawful or economically uncompetitive or burdened
with excessive potential liabilities, that users of such facilities
would be forced to develop and/or utilize services employing
more technologically advanced methods and techniques. It
also recognized that government expenditures, which this
administration is rightly dedicated to reduce, would continue
to make large sums of finance available for clean-up
operations. Many of these methods and techniques were
available, although in pilot-type stages, in the early 1970's
and Congress, with advice from EPA and other
environmental groups, believed that the implementation and
further development of these technologies could be
accomplished in a timely fashion such that a major portion
of the adverse environmental impact taking place at the
time the law was passed could be curtailed and / or eliminated
over the next decade.
Congress also recognized that the law needed public
support to make it work. Congress believed that public
support was present. This was implied through the limited
protests received from the public and the overwhelming
support of environmental groups, local and state politicians,
regulatory authorities, and the EPA. Therefore, Congress
believed that it was passing a popularly supported Act and
that its implementation would be only a matter of time
through the development of necessary needed rulemaking
and enforcement procedures. What Congress did not take
into account, however, was the developing concern among
citizens and environmental groups with regard to the siting
of new and technologically efficient facilities to replace
environmentally inefficient existing facilities. Congress
believed that the implementation of the rules would be a
public mandate. What it did not recognize is that
implementation of the RCRA rules and law would be
subject to adverse citizen pressure brought about by a public
misconception of what the RCRA rules really meant.
Citizens had the clear feeling and conception that the
development of facilities to handle potentially toxic and
hazardous wastes would cause grave and considerable
environmental problems. However, the citizens clearly were
not, and still are not, willing to accept the fact that in the main
the current disposition of toxic and hazardous waste is not
being handled in an environmentally sound manner, and
that this was a major purpose for the Act to begin with.
One is tempted to get philosophical about the solution to
the problem. That is, the employment of new and modern
technology to solve a problem perceived by Congress and
the nation in the mid-1970's. The philosophy could go
something like this: The nation, after experiencing a rapic
and great industrial revolution and becoming the mos
efficient manufacturing country the world has ever known
provided enough goods and services to raise the standard o
living to previously unknown levels and consequently thi
expectations of citizens ran somewhat ahead of reality
Much of the industrial development the country experiencec
between the early and mid-1900's occurred with minima
overall resource planning. Such a view became mon
prevalent in the late 1960's and still exists today. Mos
industries now evaluate a project on its full impact basis
That is, not only the economic merits of the process anc
technology with regard to the installation of the facility anc
! he operation of the facility, but also the social ramification;
resulting from such an operation. These results could be
environmental results, community and social results, etc
Therefore, we have a national dilemma. Simply stated, the
public perception that, "We can do anything we please to do
but not make any sacrifices whatsoever to do those thing;
that we must do, wish to do and need to do", is in flux and ii
takes time to face up to new realities.
Helping to foster this viewpoint and creating an even mon
difficult environment in which to operate, we also have the
pressures that motivate political leaders to either action 01
inaction. Politicians and those employed by them, i.e
bureaucrats, are prone to change viewpoint due to extreme
nublic pressure that they perceive to cause them potentia
political harm, even though many of the individuals anc
groups raising these concerns represent a small minority ol
citizens.
Many citizens believe that since the RCRA Act wa<
passed and states have been mandated to implement rules.
the problem has disappeared and it is no longer of majoi
concern. What the citizens do not understand is that the law
was simply the first step of a process designed to eliminate
current unacceptable practices which may lead to harmfu
results. The harm is not only from pollution of the land anc
groundwater, but also from the economic burden placed or
industry and society when pollution events cost more tc
correct than the offending company can afford.
Stablex Corporation has been at the forefront ir
attempting to establish cost-efficient environmental control
facilities designed to satisfy RCRA requirements and
mitigate against potential environmental harm by the use ol
the newest and most modern technology available for the
treatment of certain types of waste materials. The company
has been engaged for several years in the development of its
process and technology in the United States. The technology
has been employed in England successfully for the last
several years, and a major facility is planned for construction
in Canada in the near future. In each location in which the
company has attempted to begin operations, whether the
locations be in England, Canada or the United States, severe
and strong public opposition has been "part and parcel" ol
the development process. What is interesting and intriguing,
however, is the fact that the establishment of facilities in
countries such as England and Canada apparently are seen
as beneficial to the overall community in an economic and
environmental sense. The politicians and bureaucrats,
although being subjected to substantial public pressure from
relatively small groups of citizens, have listened to all citizen
complaints. They have ensured the facilities would conform
to all public concerns by adding permit amendments which
reflect the public's concern for maximum safety with
minimum risk. What has happened, however, is that in the
United States the public officials have not yet recognized the
importance of taking a firm stand to assist the development
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of facilities that are designed to answer the public need. They
believe that time will change public attitude and, in turn, the
needed facilities will be constructed sometime in the future.
Until that occurs, however, the practices and procedures that
have been of concern to citizens and government are still in
force and in progress. Furthermore, it is a matter of concern
as to whether or not the examples of Love Canal, etc. are just
tips of an immense iceberg of malpractice below the surface.
The question that should be posed in every community is do
you wish to ignore the uncontrolled malpractices still
prevalent today, only to wake up one day surrounded by
another Love Canal or do you want to participate in a
controlled, disciplined, modern technologically
administered industry in which safe methods of handling
the problems prevail?
The same environmental potential contamination which
occurred in the 40's, 50's, 60's and early 70's which brought
about the RCRA Act, still occurs because the
implementation of new technology has not taken hold. The
basic reason that the technology has not taken hold is not
because companies have not wished to spend money to
develop facilities, but because no community has been
willing to accept a facility. Therefore, corporations in the
business of converting or treating potentially toxic and
hazardous wastes and removing their potential toxicity or
mitigating it, and the generators creating the waste materials
that must be treated, as well as the citizens demanding
proper environmental treatment and disposition, and the
federal and state governments which have the structures and
the rules to implement and force such solutions, are all
caught up in the problem of the inability to act. This inability
is directly related to public pressure and concern.
It is Stablex Corporation's view that this public concern
and misconception can be dramatically changed by the
establishment of facilities to demonstrate that they can
operate in an environmentally acceptable fashion and
eliminate much of the potential hazard associated with the
disposition of wastes generated by American industry today.
Stablex Corporation
After reviewing the Introduction, it is quite possible that it
could appear that Stablex Corporation has been engaged in
a sociological development rather than a technological
development. I think we have indeed been engaged in both.
Stablex Corporation is a company engaged in the business
of converting potentially toxic and hazardous wastes that are
essentially inorganic in nature to an environmentally inert
final product. This product, STABLEX, is a material that
has been tested by several independent laboratories not
associated with Stablex Corporation. The results of these
tests and other reviews have led the United States
Environmental Protection Agency to classify STABLEX
material on an interim basis as a non-hazardous material
when produced from twenty-nine different categories of
waste materials.
The process was developed in the late 1960's and brought
to commercial fruition in the early 1970's in the United
Kingdom. After several years of successful operation, the
process was brought to North America. The process
technology, called SEALOSAFE technology, takes several
steps to accomplish. First, prior to accepting material for
processing at a process plant, the material must be tested to
determine if it can be successfully treated through the
SEALOSAFE technology. It should be noted that the
SEALOSAFE technology is geared toward, for the most
part, large-scale regional treatment facilities which take a
wide variety of potentially toxic and hazardous industrial
waste materials and combine them so that their synergjstic
properties can be utilized to decrease the costs of conversion.
Also, because of the large-scale nature of the facility, the
capital employed per unit processed is decreased to the point
that the process economics are more than competitive with
existing techniques for the disposition of industrial
hazardous wastes, namely dumping onto the ground or into
the ground. Recently, however, it has come to the attention
of Stablex Corporation that there are circumstances in
which it may be economically feasible to establish a facility
for a sole-source generator of waste materials. Usually this is
accomplished for a rather large sole-source generator such
that the economics are competitive with alternative
techniques. One thing the generator must do when
comparing competitive costs is to include the decrease in
liability through SEALOSAFE as compared to controlled
dumping. Dumping onto the ground, even with controlled
double-liner systems, runs a relatively high degree of risk of
adverse environmental impact when compared to the
conversion or detoxification of waste materials.
Since the establishment of Superfund and other funds
including certain state authorized programs, it has become
increasingly more feasible economically to establish
facilities that can travel from one location to another and
process a relatively small amount of material at each stop.
This "portable plant" approach is currently under
consideration by a wide variety of industries for several
uses. Basically, industry is examining this approach for the
cleanup of old ponds and lagoons or the conversion of
stored waste materials on a time-cycle basis such that the
materials can be converted and placed on their premises to
eliminate liabilities associated with comingling in a landfill
environment.
After the material is tested for compatibility for the
SEALOSAFE process and the successful conversion to
STABLEX material has been accomplished, the client is
given a quote for the service required. The quote can take
several forms. If it is to be a portable plant type quotation,
then personnel time on-site as well as processing costs and
material costs, etc. are taken into account. Stablex
Corporation does not license this technology and therefore
requires that the plant be operated by Stablex personnel.
There are, however, intermediate mechanisms to allow the
establishment and operation of an on-site facility to make
the facility fit into the operation policy of the host
organization. Of course, if the material were to go to a
regional treatment center, a price is given for the service,
including trucking, etc.
For the regional treatment scheme, once the material
enters the facility it must first be re-examined to determine if
it has the same quality and character as that originally
contracted for. This may also be done at an on-site type
facility. Once the cross check is complete and the material is
determined to be essentially the same, it is then accepted for
processing. If the material is not determined to be the same
as initially contracted for, and cannot be properly treated, it
is rejected. If the material is suitable for conversion it is
either sent back to the generator or a new price is
negotiated. The material is then routed to a proper storage
vessel for further treatment. Treatment may include several
steps and the first step starts with the proper storage of the
waste. Again, in a sole-source or on-site facility this process
would be easier to accomplish because the amount of
materials to be stored and pretreated would be known. If
necessary, the material is pretreated to ensure that it can be
put into a state necessary for ultimate conversion to
STABLEX. Prior to the final step in the processing
operation, waste materials which have been pretreated are
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combined with many other wastes and are then tested to
ensure that the final material ultimately made from this
mixture will meet specifications well within the EPA
guidelines for a non-hazardous material. Once this is
accomplished, the material is sent for final processing.
Final processing consists of the addition of cement and
poz/olan to the pretreated slurry. The pretreated slurry, in
combination with the cement and flyash, produces the final
STABLEX material which has the characteristics of good
structural integrity and environmental inertness. The
placement of this material is a key to the success of the
operation. Stablex practices different placement
techniques, and insists that it be involved in the actual
placement operations to ensure the satisfactory
performance of the final material. Stablex Corporation
believes it is in it's best interest and the client's best interest to
maintain the placement area to ensure the material
produced can achieve its ultimate integrity and, therefore,
provide the benefits of environmental inertness and limited
liability to the producer of the initial waste material. In less
controlled situations, generators run the risk of subsequent
site malfunction with lawsuits aimed at the financially
strong generators who have used the site in the past.
Samples are taken of the product produced and
subsequently tested. Records are kept for the authorities
and for the generator.
Siting Case Histories
With regard to the siting of a plant to convert essentially
inorganic, potentially toxic and hazardous waste material
to the non-hazardous final material, STABLEX, it is time
to turn our attention to cases where Stablex has
experienced difficulties that can be expected to be
encountered in siting such facilities. There are several
facility studies that are important and relevant to discuss.
The ones that I shall address are Groveland Township;
Oakland County, Michigan; Harris County, Texas; and
Hooksett, New Hampshire. I will briefly discuss
Buckingham County, Virginia. Also briefly discussed will
be Stablex Corporation's sister company's experience,
Stablex Canada Limited, in siting a facility in the Province
of Quebec.
• GROVELAND TOWNSHIP - OAKLAND
COUNTY, MICHIGAN
In late 1977 a delegation led by the Governor of the
State of Michigan visited the United Kingdom. This
was during a period of time when the Stablex
Corporation in the United States was being organized
by the companies which developed the SEALOSAFE
technology in the United Kingdom. After discussing
the potential for the development of a facility which
could convert potentially toxic and hazardous
inorganic materials to STABLEX with the Governor
of Michigan, Stablex Corporation shareholders, in
the United Kingdom, decided that a fertile area for
• development in the United States would be the State
of Michigan. A team was assigned for the purpose of
developing a site and beginning the construction of
the first SEALOSAFE technology facility to be
operated as a regional treatment plant in the United
States. Several contracts were made with the
Michigan State Development Authorities and the
Michigan Department of Natural Resources (DNR).
In the early part of 1978 the Michigan Department of
Natural Resources advised Stablex Corporation
representatives concerning certain areas of the State
of Michigan which were proposed for development
by the State Economic Development Authority.
After doing some preliminary engineering planning it
became evident that only one of the sites had many of
the ingredients necessary to establish a facility to
process waste materials. The particular site located in
Groveland Township, Oakland County, Michigan is
adjacent to a modern interstate highway,
approximately 35-40 miles north of the city of
Detroit, and in a major inorganic hazardous waste
generating area. The site also has a great need for
restoration, in that approximately 150 of its 200 acres
have been mined successively for over 40 years. The
pits present at the site are as deep as 50 feet and the
only realistic method available for land reclamation is
the placement of an inexpensive fill-type material to
bring the land up to grade.
The owners of the site had been in negotiations with
the local community for several years due to their
proposed development of a sanitary landfill at the
site. The Town passed some restrictive zoning
ordinances to bar the establishment of the sanitary
landfill, although the State had already issued all
necessary permits for its operation. After a lengthy
series of discussions which lead to a court trial, a
Consent Judgment was entered into by the Town and
the sand and gravel pit owner. Effectively, the
Consent Judgment ordered that the land be restored
and brought to near grade using an essentially
inorganic, non-combustible, non-flammable,
environmentally inert material. The Town thought
the language utilized in the Consent Judgment would
clearly obviate the establishment of a sanitary landfill.
Stablex Corporation, after negotiations with the land
owner, signed an Option Agreement to purchase the
land. Stablex Corporation then approached the
Town after previous discussions with state
authorities. The first meeting, which was between a
few Town Elders and some interested citizens, was
not conclusive. A second meeting was called at which
time Stablex Corporation could more fully develop
and explain its plan. Prior to the second .meeting
being called, the Town decided that it did not wish to
have a facility located within its borders that would
process potentially toxic and hazardous material.
Although they did not fully understand the proposal,
the mere hint of the term, waste, especially toxic and
hazardous, resulted in the Town having no part of the
proposal. Stablex Corporation met with local
environmental groups, including the Audubon
Society, and several Michigan groups organized for
environmental protection, and explained its proposal
and met with little resistance. As a matter of fact,
there was some outright support, although low key.
The state government accepted Stablex Corporation's
Environmental Assessment Statement which they
had required to begin the permitting process. Next
Stablex held a small briefing at which it discussed
with the press its plans for the Groveland site. The
briefing included models, pictorial representations,
photos, etc. of the proposed facility and other types of
facilities that were already in operation. No
representatives from the Town came to this briefing
although they were informed of it.
The Township next organized a meeting to be held
at a local high school at which Stablex Corporation
could present its story to the public. Approximately
550 people attended this meeting held at a local high
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school. Again, a major presentation was launched by
Stablex Corporation explaining in reasonable detail
the approach and the potential benefits to the
community. As expected, the meeting was tense
although reasonably controlled. The obvious tone of
the people present was wholly and totally against the
Groveland facility for the treatment of potentially
toxic and hazardous materials and the reclamation of
the ground with a non-hazardous final product. After
several hours of discussion and questions and
answers, it became clear that the individuals present
were, for the most part, against the establishment of
the facility.
Stablex Corporation next proposed to the Town
Planning Board the establishment of the facility and
submitted a Siting Plan and a Mining/Restoration
Plan. The two separate plans were required by town
ordinance. Meanwhile, prior to Stablex submitting its
plans, the Town passed ordinances effectively
restricting the operation of a facility such as the one
Stablex was proposing by establishing what they
called a "special waste category". The special waste
category was established for material which was
produced from a variety of materials which were at
any time classed as waste. Even if the material
produced was non-toxic and non-hazardous, it
could not be placed in Groveland Township. This
ordinance clearly meant to stop the establishment of
the facility that Stablex proposed.
Stablex was rejected by the local Planning Board in
its request for the establishment of the facility.
Stablex had a dilemma. Should it leave the
community and attempt to establish a facility
elsewhere or should it seek a remedy by asking the
Court to enjoin the Township from interfering with
its lawful rights to establish a facility which was in
accordance with all the pertinent rules and
regulations as they existed in the town at the time they
were initially applied for. Stablex's thinking was that
it was necessary to seek relief against the Town
because if it did not, then any other town wishing to
stop the establishment of a Stablex-type facility could
merely do the same thing, i.e. simply say they didn't
want it, and then Stablex would find itself in the same
position every place it went, effectively eliminating its
business potential.
A motion was filed in the local Circuit Court in
April, 1979 and lasted until April, 1980. By the time
the Court reached its verdict, April, 1980, Stablex
Corporation had spent over a million dollars
developing the Groveland site, especially with regard
to permit applications, court proceedings, etc., and
was well on its way in the permitting process. The
local Circuit Court found in Stablex's favor and
issued an order enjoining the Township from
interfering with Stablex in establishing a facility, and
which stated that STABLEX material produced from
such a facility is a non-waste material, a material that
could be used for reclamation. Between April and
November, 1980, Stablex Corporation had to go to
court to force the State of Michigan to issue permits
to it. The State of Michigan has decided that all the
permit applications that Stablex had submitted to it
were complete, but were stalling on the issuance of
permits, primarily in Stablex's opinion, for political
and other reasons especially associated with citizen
pressure. Again the Circuit Court found in Stablex's
favor and ordered the DNR to issue permits to
Stablex, allowing it to begin the construction of its
facility. These permits were issued prior to November
18, 1980 which effectively grandfathered the Stablex
facility as an existing facility under the RCRA rules.
It should be noted that this exclusion from the
RCRA rule process does not imply that Stablex
Corporation is exempted from constructing the
facility in accordance with RCRA. As a matter of fact,
Stablex was issued an Act 64 permit by the State of
Michigan. The permit was issued under a law passed
requiring that Act 64 rules were to be modeled after the
RCRA statutes. The unique part of the permits issued
to Stablex by Michigan DNR was that the State
recognized the waste treatment and reclamation center
could be permitted with two separate permits. First a
permit to treat and convert potentially toxic and
hazardous waste material to a non-hazardous
material, STABLEX, and second, a placement area
which could accept the non-hazardous STABLEX
material as a result of the technology employed in the
processing facility. To the best of my knowledge this is
the first time a state has taken this stand.
Stablex Corporation was now armed with two
permits. One, a permit to construct a toxic and
hazardous waste treatment facility to convert
inorganic materials to STABLEX material; and
second, a placement area which could accommodate
the STABLEX material produced from this facility
and in turn reclaim the land in accordance with the
Consent Judgment the Town and land owners had
agreed upon.
The EPA next received a request from Stablex
Corporation to delist STABLEX material and the
State of Michigan requested EPA for rapid action to
classify STABLEX as non-hazardous material. EPA
issued a temporary delisting in November, 1980 which
meant that STABLEX produced from twenty-nine
different categories of listed toxic and hazardous waste
is considered non-hazardous. This corroborated the
State of Michigan's stand with regard to the issuance
of permits for land reclamation purposes.
Next, the Town appealed the Circuit Court
decision and asked the Appellate Court to enjoin
Stablex from continuing any construction during the
appeal period. The Appellate Court granted the
Township's request for injunction and Stablex was
barred from continuing construction in December of
1980.
For Stablex to continue construction, the Appellate
Court had to act. Stablex was at a standstill. Stablex
asked the Township if it would consider negotiating to
reach a mutually acceptable and agreeable solution.
They refused. In May 1981 the Appellate Court found
in favor of the Township and overturned the Circuit
Court decision saying that if certain evidence had been
introduced in the lower court, its verdict would have
been different. This, in Stablex's opinion, is clearly
against the admissible evidence rules as Stablex
understands them and to clarify the issue, Stablex has
lodged an appeal with the Michigan Supreme Court.
To date, Stablex has spent or committed to the
Michigan Project development about $4 million.
There is no modern treatment facility in the State of
Michigan. There is no placement area which places
exclusively detoxified material in Michigan. All
material placed in Michigan is placed in either a
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sanitary landfill or secure landfill. Many wastes are
trucked out of the State of Michigan at great expense
to Michigan industry. All the people employed in the
Groveland area owe their livelihoods to Michigan
industry. The Stablex facility to be located in
Groveland, Michigan would be an employer of people
and provide a reasonably high tax base because of the
substantial capital investment Stablex had committed
itself to, $20 million. So to date, four years after the
start of discussions with regard to the establishment of
a facility meeting RCRA standards in the State of
Michigan, no facility has been constructed, but there is
a facility with permits that can't be constructed.
Stablex has every intention to see its case through
the Michigan Supreme Court and believes the
outcome will affirm its arguments so that it can get on
with helping to solve one of the most enormous
problems confronted by the State of Michigan, the
safe treatment of toxic and hazardous wastes.
• HARRIS COUNTY, TEXAS
In 1979 Stablex Corporation proposed to the Gulf
Coast Waste Disposal Authority, GCWDA, that the
Authority consider entering into an agreement with
Stablex to allow Stablex to operate a toxic and
hazardous waste treatment facility at a Gulf Coast-
owned site. After due consideration, the GCWDA felt
it would be in the best interests of the citizens of the tri-
county area in which it has semi-governmental
authority, to establish a regional treatment facility
which could treat and detoxify a wide variety of waste
materials, some of which may be inorganic in nature.
The Authority went on a world-wide search for
technologies to incorporate into this facility and
studied many different and varying treatment methods
either in use or proposed. After their exhaustive study,
and several visits to facilities that were operating in
various parts of the world, GCWDA chose Stablex
Corporation to establish a facility for the conversion of
potentially toxic and hazardous inorganic materials to
the non-hazardous STABLEX material. They also
chose another processor for incineration, and plan to
choose other companies to deal with oil/water-
separation, solvent recovery, etc. Stablex Corpora-
tion, GCWDA, and the incinerator processor
collaborated to submit permit documents to the State
of Texas. The permit documents were submitted in
mid-1980 and the relevant Texas authorities agreed
the documents were in conformance with necessary
standards for issuance. However, part of Texas law
includes the holding of a series of several meetings at
which the public can express their views, either
technological or sociological. GCWDA, believing that
it had political integrity on its side, felt the hearings
would not be a major roadblock to the establishment
of the regional treatment facility which was to be
located at a site next to the Ellington Air Force Base, in
an area previously used for a sand and gravel mining
operation. No residences were close by and the land
was used for reasonably low valued uses. A
groundswell of opposition quickly developed. Among
the opposition leaders were competitors who were
concerned with the competitive .nature of the facility
proposed by the Gulf Coast Waste Disposal
Authority. One of the competitors actually went to
such lengths as to hire an individual to travel from
place to place in Texas and throughout the United
States, following Stablex Corporation developments
and complaining about Stablex Corporation. This
individual went as far as to submit to the U.S.
Environmental Protection Agency a series of
newspaper clippings as evidence of why Stablex
Corporation should not be granted a temporary
delisting for its material. The newspaper quotations
and clippings, although containing not a shred of
technical data or evidence, have of course been
accepted by EPA in their evaluation only because of
their sincere desire to ensure that all Americans have
the opportunity to comment on environmental
matters. This particular approach, although noble and
worthy, needs in our opinion to be re-examined in
some detail. The question arises as to what difference it
makes if a newspaper in some part of the county
believes that a facility may or may not do something
good. That's an opinion and perfectly acceptable and
reasonable in today's environment and society, but
opinions are not necessarily fact and in our opinion
fact controls the issuance of permits. Technological
success in a social framework is the ultimate goal.
Because of the major uproar caused by the
announcement of the planned facility adjacent to
Ellington Air Force Base, the two companies and Gulf
Coast Waste Disposal Authority re-examined their
proposal for the establishment of the Ellington facility.
On re-examination it was ielt that perhaps the
proposed facility should be moved to a more
industrialized area. After spending something on the
order of $1 million in the initial site development, it
was decided to abandon the Ellington site and move to
a new site in a more industrial area, the Bay Port site.
The site selected was announced in October 1981.
Although no organized opposition was expected,
severe opposition is forming and is currently
mounting. I can't report to you at the present time the
actual outcome of this particular development, but I
can only say it appears to be a repeat of the Ellington
situation. The unfortunate thing involved here is that
the State of Texas was actually involved, although
peripherally, through a State of Texas organized
corporation - Gulf Coast Waste Disposal Authority -
in the site selection process and the permitting process.
The state of Texas has so far been barred from the
establishment of a facility that is so much needed in
this area.
• HOOKSETT, NEW HAMPSHIRE
In late 1979 Stablex Corporation began to study the
New England area as one that was in need of a facility
to treat and process inorganic materials to STABLEX.
After a careful selection process, Stablex came to
believe that the best location for the establishment of a
regional treatment facility was the State of New
Hampshire. Visits were made to the State Office of
Solid Waste. The State Office of Solid Waste was quite
helpful and receptive to Stablex Corporation's visits
and inquiries. Stablex also visited the State Economic
Development Authority and discussed with them tjie
development of a site to treat and process waste
materials. Presentations were made to the State Senate
Committee responsible for solid and hazardous
wastes, as well as to several business and industry
groups. After many discussions and considerations, a
site in a town located outside Manchester, New
Hampshire, in Hooksett, was chosen. The Town
Selectmen were visited and informed of Stablex's
selection. The Selectmen were in reasonable
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agreement that the Stablex proposal was realistic,
reasonable and doable in Hooksett. A meeting was
held at the local high school where Stablex presented
its story and answered several questions of concerned
citizens. No apparent opposition was noted at that
meeting. As time went on, however, opposition began
to mount, and by the time Stablex Corporation was in
the process of preparing its submissions for Planning
Board approval, substantial opposition existed.
Stablex Corporation participated in several studies
and trips organized by the people in the State of New
Hampshire. First, a group of citizens from the Town of
Hooksett visited the facility at the expense of the New
England Regional Commission, which is a public
entity located in Boston, Massachusetts. The citizens
came back reasonably impressed, feeling that the
Stablex facility could indeed do what Stablex claimed.
That is, convert toxic and hazardous waste materials
to a non-hazardous final product. Along with the
citi/ens were representatives from the University of
New Hampshire who wrote a report which said that
"Based on an extensive analysis of existing data
concerning the STABLEX process for solidification of
hazardous waste and discussions with experts in the
hazardous waste disposal field, it is our feeling that the
Stablex proposal for Hooksett, New Hampshire will
likely result in little impact on the environment." . . .
"In summary we feel that all existing data at our
disposal indicate that STABLEX is an environ-
mentally safe material, that it will not pollute the
groundwater, and that the Hooksett site is amenable
to this process." Additionally,' the newspapers were
reasonably supportive to the establishment of the
facility in Hooksett, and it was Stablex's opinion that
the facility would be approved by the Planning Board.
However, a visit was made by three officials from the
State of New Hampshire to facilities utilizing
SEALOSAFE technology in England. Prior to that
visit Stablex carefully explained to these visiting
officials that of the facilities that they were to visit, one
facility was treating and processing inorganic
materials and producing STABLEX material. The
other facility had at one time done this, but since that
time it had changed operation and was processing
both organic and inorganic material, and -is not
producing STABLEX product. The officials insisted
on visiting both facilities and Stablex concurred,
because if Stablex did not it would have been accused
of hiding something.
Along with the New Hampshire State authorities
was a visitor from the State of Louisiana hired by the
State of Louisiana to go and visit Stablex's facilities for
evaluation purposes. First the individuals visited a
facility located outside of Thurrock, England which
processes only inorganic material. The State of New
Hampshire visitors, although informed prior to their
trip that it would be extremely difficult to take samples
back to the United States because of having to deal
with another company's management, insisted that
samples be taken and as a matter of fact, took samples
without permission from anyone. When it was noted
to them that they had taken an unauthorized sample,
they refused to give it back. This, of course, caused
great consternation and rather than letting this
develop into an argument, Stablex officials felt it was
best to allow the New Hampshire officials to take their
sample because Stablex Corporation officials knew
and understood that the sample was perfectly safe and
acceptable under the U.S. EPA rules. However, just to
make sure the data developed by New Hampshire
could be corroborated, the Stablex officials asked that
half the sample be given to them for testing at the
Thurrock laboratories that day. The testing was done
in front of the New Hampshire officials. The data
showed that the material passed the EPA require-
ments as a non-hazardous material.
The New Hampshire officials also visited the other
facility that I mentioned earlier which processes both
organic and inorganic wastes. On their return to the
United States a report was written which was
damaging to Stablex Corporation in that the visitors,
for example, reported that leaking drums, old bags,
and puddles were observed. Now anyone who has
visited any processing plant, especially a plant that
processes toxic and hazardous wastes, will know that
wastes are sometimes not shipped in the newest type
containers. Because a drum is leaking does not mean it
will contaminate anything. The facilities are equipped
with bermed areas to insure that leaks and spills are
contained and routed to processing areas. The old bags
may have been bags of material that were rejects from
a production process and sent to the waste
management facility for incorporation as a treatment
chemical. The puddles could have been caused by
leaks from drums, etc., which were contained behind
bermed storage areas. The New Hampshire officials,"
however, avoided reporting that they took a sample
and that the sample was tested and proved to be
satisfactory. It was clear to Stablex Corporation
officials that the individuals visiting from the State of
New Hampshire were not interested in the truth, but
were interested in creating a case to show that the
SEALOSAFE process and its operation in England
were questionable. It should be noted that the
Louisiana consultant wrote a positive report which
was dramatically opposite to the New Hampshire
authorities' report. In Stablex's opinion, much of the
reason the Township Planning Board ultimately
rejected Stablex's proposal for the construction of a
facility in Hooksett was due to the State of New
Hampshire officials' report. Additionally, the Town of
Hooksett followed in the footsteps of Groveland
Township in that they passed an ordinance seeking to
bar the disposition of toxic and hazardous wastes of
any type in the Town of Hooksett unless those wastes
were generated within the boundaries of the Town of
Hooksett. Stablex Corporation, after being rejected
by the Planning Board, challenged the ordinance and
the rejection of the Planning Board in New Hampshire
Superior Court. At present, the Court is determining
the issuance of whether or not the ordinance passed
was valid. It should be noted, however, that the State
did file a Friend of the Court Brief in favor of the
Stablex position that the ordinance passed by the
Town was invalid. The State argued that if the Town
of Hooksett were successful in utilizing this type of
procedure to regulate the processing and treatment of
potentially toxic and hazardous wastes, there would be
nothing to stop every other town in New Hampshire
from doing the same and therefore, the entire
framework of the State rules and regulations
concerning the disposition of toxic and hazardous
wastes would be moot.
Stablex believes it will prevail in court with regard to
39
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the issue of the ordinance. Stablex wishes to construct
and operate a facility in Hooksett at the earliest
possible time. To this end, Stablex filed a set of permit
applications in September of 1980. The permit
applications were first reviewed by the New
Hampshire authorities in June of 1981. Immediately
after the New Hampshire authority review, Stablex
was informed that the permit applications which had
been sitting on their desks for nearly eight months were
incomplete and further information was requested.
Stablex provided such information in November of
1981 and is currently waiting to hear from the State of
New Hampshire if the applications can now be
considered complete. In the meantime, New
Hampshire industry has no outlet in the State of New
Hampshire for the potentially toxic and hazardous
wastes that it generates. Wastes must travel in some
cases hundreds of miles for ultimate disposition. This
is extremely costly for the industry of the State of New
Hampshire, but to our surprise no industry in New
Hampshire has raised its voice in protest over the
actions the State has deemed necessary to impose on
Stablex.
Stablex continues to pursue its objective in New
Hampshire. That is, the establishment of a plant to
treat and convert potentially toxic and hazardous
waste to STABLEX material, and the corporation is
planning to construct such a facility as soon as
reasonably possible.
• BUCKINGHAM COUNTY, VIRGINIA
The case of the establishment of a facility in the
County of Buckingham. Virginia is most interesting.
Stablex discovered in May of 1981 that a permitted
facility existed in Buckingham County, Virginia which
was authorized by the EPA and the State of Virginia
to accept various types of potentially toxic and
hazardous wastes for disposal. The disposal practiced
was, and still is, land placement in clay-type soil with
the standard coverage procedures. The material being
accepted at this site consisted mainly of furniture
industry wastes, mainly organic in nature. Stablex
Corporation believed that the permits that the site
operator had could be modified such that a Stablex-
type facility could be constructed and operated.
Stablex believed that its approach to the Buckingham
Site would be extremely beneficial to the residents of
Buckingham County and to the State of Virginia. The
reasoning went something like this - The site is
currently being used for ordinary dumping. Stablex
brings a high-technology processing facility to the site
to convert various types of toxic and hazardous wastes
to a non-hazardous material, thereby decreasing the
likelihood of any adverse environmental impact
resulting from the use of the site. Additionally, the
State of Virginia benefits because a facility offering
services to treat inorganic materials would be present.
The problem Stablex foresaw, however, was the
site had been used for a number of years for the
placement of this furniture industry type waste in
addition to ordinary garbage and refuse. A potential
liability existed, on Stablex taking over the site.
Stablex felt that it would be in their best interest as
well as the State's best interest to attempt to mitigate
against this potential liability prior to proceeding.
Stablex approached the State and suggested that the
State purchase the site and Stablex then lease from
the State on a long-term basis, thereby having the
State then accept the liability for the older sanitar
landfill/furniture waste placement area. The Stat
discussed this approach with Stablex Corporatioi
several times and believed that it was feasible an<
reasonable. Stablex Corporation discussed it
approach with the Governor of the State of Virginia
who put his support directly behind the project.
All that was left to do was to have the State Boan
of Health approve the arrangement to enter into a tri
party agreement between Stablex, the site owner am
the State for the State to purchase the land anc
Stablex to lease it on a long-term basis.
The State next went to the County and discussec
with the County the plan to acquire the site and tc
allow Stablex to construct its facility and operate
there. The local officials were immediately concerned
and alarmed. It's uncertain whether their concern and
alarm was due to the fact that they were not fully
informed from the very beginning about the project,
or that the project was about to be undertaken
without their advice and consent. At any rate, the
officials sought an injunction to stop the State from
acquiring the site. The local judge granted the
injunction. The injunction was challenged in the
Virginia State Supreme Court by the State Health
Board to proceed with its plan to acquire the site and
have Stablex begin its site studies and specific
permitting for it, followed by plant construction.
During this time a groundswell of public opposition
developed. Everyone apparently missed the point that
the site had already been used for several years as a
toxic and hazardous dump. The process proposed for
the site was an upgrade to the site with substantial
capital investment being committed to it. This
however was of no importance to the opponents of
the site. The opponents eventually forced the State
Health Board to enter into a study to determine which
sites in the State of Virginia could be utilized for the
development of a toxic and hazardous waste
placement area in the State of Virginia. The study is
planned to take at least six months.
When this happened, the Buckingham County
officials approached the site owner and offered to buy
the land from him for their own use, thereby
circumventing any potential use by Stablex or the
State for the establishment of a SEALOSAFE-type
facility. The situation as it presently stands is in flux
and it is difficult to report on the ultimate outcome of
this development. All that can be said, however, is
that this was a development that had the support of a
Governor and of a Health Board. Such support
withered in the face of the enormous public pressures
placed upon these officials by the citizens of
Buckingham C ounty, a small Virginia county. The
difficult point for Stablex to understand is that the site
is already utilized and has been for several years as a.
dump. Stablex wished to upgrade its use, thereby
minimizing the problems that could be generated as a
result of the continued operation of this type dump.
That has not occurred as yet.
What Can We Learn?
With the case histories cited in the previous section as a
basis for at least an understanding of the experience that
Stablex Corporation has been through in attempting to
permit a RCRA type facility to answer the crying need to
develop proper and economically competitive control
40
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facilities, it may be possible to extract some kernels of
knowledge.
In my opinion it appears that technology really is not the
determining factor in siting a facility. True, technology is
the motivating force behind a company such as Stablex in
attempting to develop its business, which offers an
environmentally acceptable solution to ordinary dumping.
However, the more fundamental hurdle is to convince local
populations as well as their political leaders and the
bureaucrats who work for them that the installation of such
facilities will in the end be in the public's best interest. The
exact methodology to convince people to accept a good and
worthy solution to a continuing problem is extremely
complex.
Stablex is a company wishing to spend its own capital
resources to develop an industry to serve other industries
and, in turn, people. It is caught up in the mid-1900's
syndrome. That is, growth at any price is unacceptable, and
therefore any new facility that may be productive in nature
is looked on with great suspicion. If one can examine the
development of recent projects within the United States, it's
reasonably clear that many of them have been substantially
curtailed or in come cases stopped completely by
overwhelming public opposition, even at the cost of jobs
and economic viability to the communities which opposed
them. People are convinced that the "pursuit of the good
life" could be severely hampered by the development of
what they perceive to be unwelcome neighbors in the form
of industrial corporations which add to the overall wealth of
the community and society. Stablex Corporation is caught
up in the same maelstrom of debate and philosophy. It goes
unrecognized, however, that hand-in-hand with the pursuit
of the good life are the services necessary to ensure it can
continue. Services as essential as garbage collection, water
supply, sewage, food, electricity and heat must continue.
Many of these activities are productive, profit-making
enterprises and accepted as necessities by society. Some of
them may be considered repugnant in nature, but it still is
necessary and important to continue the supply of their
services. Society considers the dumping of garbage and
refuse a repugnant but necessary service. Towns usually
allow the operation of refuse disposal areas only after they
have been forced into this solution and no alternatives exist.
Additionally, the older placement areas utilized for the
disposal of toxic and hazardous wastes are usually located
in an outlying area or in a depressed area where the local
populous is either not present or not as vocal as those in
more affluent areas. Stablex Corporation, although
providing a service much more technologically advanced
than dumping, is cast in the same role as the garbage dump.
Because of this, and because there is no real need in many
communities to specifically have a toxic and hazardous
waste treatment and resultant non-hazardous material
placement area located within the borders of the town, the
town fathers usually take the more expedient way out and
side with the small but extremely vocal minority that for the
most part is committed to clearly resist any change.
One is tempted to consider the cessation of activities
leading to the development and commercial operation on
new technologies and their implementation for waste
disposition. The result of this would be continued dumping
practices which society has recognized as unacceptable, but
has not yet accepted their responsibility of dealing with it.
It is Stablex's view that the most essential point in the
location and subsequent development of a facility to treat
toxic and hazardous wastes and to change their character to
a more environmentally acceptable form, is the support of
committed local citizens and their political leaders to ensure
that overriding community needs can be answered. This
takes courage. It takes conviction and it takes the
understanding and belief that unless the problem is solved
somewhere in a satisfactory manner, it will continue to be
swept under the rug in an unacceptable fashion. Stablex
seeks to work with the community leaders to help them
understand the nature of its process technology and what it
wishes and plans to do. Stablex stands ready to assist the
community and provide benefits to them as a result of their
allowing these facilities to be constructed.
We are at a critical juncture. Siting facilities is the
fundamental issue. To date, we are unaware of any proven
means to develop and locate a facility. Stablex certainly has
no wish to continue its development through court suits. It
believes in the end it will prevail, but look at the total cost in
continued improper dumping of wastes.
PROPOSED SOLUTIONS
The only solution I can offer is a plea for you to think
through in a thorough, logical, and concise manner the
problem as it currently exists, their need for a solution, and
the proposed solution. Many of you who have read this
paper will decide that the problem is not really your
problem. Others will feel that their particular toxic and
hazardous waste problems are being adequately taken care
of. Still others will decide that someone else will take care of
the problem and the issue. I am interested in talking to those
few of you who have a commitment to institute modern
methods designed to minimize liability and environmental
harm.
The solution really lies with you the reader. It lies with
your communities in recognizing the need and being
courageous enough to accept the challenge of providing a
solution. It lies with your industry, in understanding its
liability exposures and its potential for contingent liabilities
and its willingness to become good citizens in their
communities. In addition, it lies with industry in
recognizing that the problem is not solved by shipping
wastes 100 or 1,000 miles away and not really
understanding their ultimate disposition.
CONCLUSION
In this paper I have introduced to you what we believe to
be the origin of the problem of industrial toxic and
hazardous waste disposition. I have explained something
about Stablex Corporation, its development and its
business. I have told you about how we have gone about
attempting to implement our business, which in effect was
created as a result of the passage of the RCRA Act. I have
reviewed for you our long and arduous siting process in
Groveland, Michigan which resulted in long litigation and
is still unresolved even after four years of bitter debate and
millions of dollars having been spent. I have cited the
innovative approach that Stablex Corporation and the Gulf
Coast Waste Disposal Authority took to place a regional
treatment center into operation and the bitter opposition
that emerged by not only well-meaning citizens, but also by
competitors who had a significant economic stake at risk.
I have briefly discussed how reports that are written by
well-meaning state officials can amplify certain facts and
leave out others and be accepted as the total truth rather
than as an edited version of the truth. I have discussed
how the support of high-ranking state officials, for example
the Governor of the State of Virginia, can lead to
disappointment and no progress.
Stablex believes it can provide a part of the solution. We
41
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have never said that we are the entire solution, nor do we
pretend that we will ever be. If Stablex had ten times the
capital resources presently available to it. it still could not
provide all of the services needed to adequately treat and
place the materials previously discussed. Therefore, we seek
a start. We have made the offer that we will build a plant
anywhere there is a reasonable market, at our own expense,
to demonstrate that we can do exactly what we say. We
make the offer again. We ask for assistance from
community leaders and industrialists who recogni/e that
now is the time to act to solve this most pressing
problems, the adequate disposition in an environmental
acceptable fashion of potentially toxic and hazardoi
wastes generated by industries serving all Americans ar
which industries allow us to enjoy the standard of living v
currently have.
The work described in this paper was not funded by t,
U.S. Environmental Protection Agency and therefore t>
contents do not necessarily reflect the views of the Agent
and no official endorsement should be inferred.
42
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Disposal: What Does It Really Cost?
Donald W. Smith, II*
Clarence H. Roy, Ph. D.
ABSTRACT
In past EPA and AES Seminars the electroplaters have heard a number of papers
dealing with in-plant modifications, conservation of water and chemicals, ways to minimize
sludge and how to recover water and chemicals by a variety of methods. Despite aB the
information presented over the years very little has been done in the majority of plants to
implement the recommendations provided by these papers. While some of the recovery
technology is quite expensive and might be rejected on budgetary grounds, this argument
does not prevail for many of the inexpensive recommendations. It appears that indifference
or lack of motivation on the part of many platers has inhibited a serious attack upon waste
in the plating room. These same people voice complaints about the high capital costs of
wastewater treatment equipment.
Waste is stiff the crux of the matter. Water and chemical waste impacts not only upon the
size and cost of the treatment equipment, but also upon manufacturing costs and waste
treatment costs. Some say that inactivity or indifference indicate a lack of motivation. This
paper presents motivational material in the form of dollars and cents figures for plating
bath make-up costs, together with chemical treatment costs, sludge generation rates, and
disposal costs.
The motivation needed to persuade the metal finishers to
conserve and/or recover chemical values must reside in the
realization of the real costs of waste. The initial cost of a
chemical bath is only a fraction of the costs associated with
chemical waste. The term "chemical" is used here because as
will be seen, it is not just metals that are involved in the cost
of wastewater treatment. Admittedly, electroplating baths
represent a significant cost to the metal finisher, and it is
these make-up costs that will be examined first.
The bath make-up cost for a representative chromium
plating bath is shown on a dollar per gallon basis in Table 1.
The formulations presented in this paper are largely of the
handbook variety and the costs presented are generic prices
as prevailing in November 1981. It might be said that make-
up costs would be higher had proprietary prices been used.
The reader would be advised to compare the composition
and costs presented here with those actually experienced in
his plant.
Most readers are well aware that the hexavalent
chromium employed in chromium plating requires
reduction to the trivalent state prior to precipitation. Table 2
summarizes some of the most commonly used chemical
reduction methods, and shows some of the treatment costs
associated with the various methods.
There are some surprising differences in treatment costs,
which may cause some to reconsider previous attitudes.
Keep in mind at this point that we have not yet reached "the
bottom line," and that there are more cost factors to be
added.
Note that the treatment costs refer to a nominal dragout
rate of one gallon of plating bath per hour. In order to obtain
* Donald W. Smith, II
Clarence H Roy, Ph D
Aqualogic, Inc
Bethany, CT
real treatment costs, the reader need only multiply (or divide
as the case may be) by the actual measured dragout rates
prevailing in his operation. A number of papers and articles
have described ways to measure dragout rates, but
essentially all rely upon measurement of metal concentration
in a fresh water rinse tank after one or more racks or barrels
have been processed. If the reader really wants to know how
much waste is costing, he would be well advised to determine
dragout rates for all process tanks. Motivation for this
activity will be developed as this presentation progresses.
Many will say they can't be bothered with all that fooling
around and the expense of doing all those chemical analyses:
but the effort and expense may well be returned by
motivating changes in wasteful practices.
Just as hexavalent chromium requires pretreatment, most
readers are also well aware that cyanides require oxidation
prior to precipitation of the metal content. In order to
establish base costs, Tables 3, 4, 5, 6 and 7 present make-up
cost figures for common cyanide baths on the same one gal-
lon basis as presented previously. The silver and gold baths
are so expensive that no one should need encouragement to
recover these values, yet some stupidity is still prevailing with
waste of these metals. The cost of treating silver and gold
solutions will not be considered here, in the hope that after
seeing these make-up costs, silver and gold will not appear in
plant effluents.
The oxidation of cyanides is usually accomplished by
alkaline chlorination using either chlorine or sodium
hypochlorite. The chemistry of the reactions involved are
summarized in Figure 1. Notice that the oxidation of cyanide
to carbon dioxide (carbonate) and nitrogen proceeds in two
stages. The first stage, conversion of cyanide to the
intermediate cyanate, is usually acceptable treatment for
small (under 10,000 gallons per day) dischargers to POTW
sewers. Larger dischargers and stream dischargers are
usually required to apply the two stage oxidation, and
43
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Formula
CrO,
H SOj
Table 1
Chrome Bath
Make Up
Cone (oz/gal)
25
025
Total Cost/Gallon
Cost/Gal
$234
$0.01
$235
Table 2
Treatment Costs
1 Gallon Chrome Plating Bath
Treatment Chemical
AMI (Ibs) Cost Total Cost
Ferrous Sulfate + Sulfunc Acid 6 76+2 38 $1 49+$0 11 $160
Iron + Sulfunc Acid 045+238 005+011 016
Sodium Bisulphite + Sulfunc Acid 1 26+060 055+003 058
Sulphur Dioxide 078 017 017
Formula
Zn(CN):
NaCN
Na2CO,
NaOH
Table 3
Zinc Bath-Cyanide
Make Up
Cone, (oz/gal)
4
2
14
13
Total Cost/Gallon
Cost/Gal
$0.48
$0.09
$0.21
$0.24
$1.02
Figure 1
Cyanide Oxidation Equations
1. NaCN + 2NaOH + CI2 -
NaCNO + NaCI + H2O
2. 2NaCNO + 4NaOH + 4CI2 -
2CO2t + N2t + SNaCI + 3H2O
3. 2NaCN + 10NaOH + 5CI2 -
2NaHCO3 + N2t + 10NaCI + 4H2O
4. 2NaCN + SNaOCI + 2NaOH -
2Na2CO3 + N2t + SNaCI + H2O
Table 4
Cyanide Copper Bath-Make Up
Formula
CuCN
NaCN
Na2CO,
NaOH
Rochelle Salt
Cone, (oz/gal)
3.5
4.6
4.0
0.5
6.0
Total Cost/Gallon
Cost/Gal
$0.61
0.19
0.06
0.01
0.62
$1.49
Formula
CdO
NaCN
Na:CO,
NaOH
Table 5
Cadmium Bath
Make Up
Cone, (oz/gal)
3
10.4
6.0
1.9
Total Cost/Gallon
Cost/Gal
$0.55
$0.43
$0.09
$0.04
$1 11
Formula
AgCN
KCN
K:CO,
Table 6
Silver Bath
Make Up
Cone, (oz/gal)
4.8
8.0
2.0
Total Cost/Gallon
Cost/Gal
$47.18
$ 0.69
$ 0.06
$47.93
Table 7
24 Karat Gold
Bath-Make Up
Average Concentration Au
Average Price Au
Cost/Gallon
1 oz/gal
$450.00/oz
$450.00
economic impact of this additional treatment is particularly
obvious. Treatment costs for one gallon of plating bath with
both single and two stage oxidation are tabulated using both
chlorine gas and sodium hypochlorite in Tables 8,9 and 10.
Table 11 summarizes the costs shown in these tables. The
reader can, as with previous tables, compute actual
treatment costs for his specific situation.
In order to compare cyanide versus non-cyanide plating
baths, with regard to first costs and treatment costs, Tables
12 and 13 present non-cyanide bath make-up costs on a
gallon basis for zinc and copper. While these formulations
may not agree with reader's preferences, they provide a
working basis for the treatment and disposal costs to be
presented. Table 14 presents make-up costs for a nickel bath
to round out a fairly representative selection of metals and
baths. The theoretical quantities and costs for both lime and
sodium hydroxide required to precipitate each of the metals
given in the formulations at the rate of one gallon per hour
for eight hours is given in Table 15. Note that these figures
are theoretical and in actuality more alkalinity is required. If
44
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Table 8
Treatment Cost
1 Gallon Zinc Cyanide Plating Bath
1st & 2nd 1st & 2nd
1st Stage 1st Stage Stage Stage
Treatment CN TMT CN TMT CN TMT CN TMT
Chemical AMT (Ibs) Cost AMT (Ibs) Cost
Sulfuric Acid
2nd stage CN tmt — — 0 01 $0 01
Sodium Hydroxide
1st stage CN tmt using
Cl: 056 $008 — —
1st & 2nd stage CN
tmt using Cl: - - 139 021
1st & 2nd stage CN
tmt using NaOCI - - 015 002
Chlorine
1st stage CN tmt 050 013 — —
1st & 2nd stage CN tmt - - 122 032
Sodium Hypochlorit-5
1st stage CN tmt 051 031 — —
1st & 2nd stage CN tmt - — 1 29 0 77
Table 9
Treatment Cost
1 Gallon Cyanide Copper Plating Bath
1st Stage
Treatment CN TMT
Chemical AMT (Ibs)
Sulfuric Acid
2nd stage CN tmt —
Sodium Hydroxide
1st stage CN tmt using
Cl: 065
1st & 2nd stage CN
tmt using Ch —
1st & 2nd stage CN
tmt using NaOCI —
Chlorine
1st stage CN tmt 0 58
1st & 2nd stage CN tmt —
Sodium Hypochlorite
1st stage CN tmt 0 60
1st & 2nd stage CN tmt —
1st & 2nd
1st Stage Stage
CN TMT CN TMT
Cost AMT (Ibs)
— <0.01
$0.10 -
- 1 62
- 0.17
015 —
- 1 43
036 —
- 1 50
1st & 2nd
Stage
CNTMT
Cost
$0.01
024
003
0.38
090
lime is used, the excess required will be much more
significant, especially when the sludge accumulation factor is
considered. Table 16 shows actual sodium hydroxide
consumption figures for three bath formulations given
previously.
While considering real treatment costs the reader must not
overlook the costs associated with the disposal of acids and
alkaline solutions. Table 17 presents a chart that the reader
can use to calculate these costs that are often neglected. The
table provides data concerning the amount of caustic or lime
required to neutralize 100 pounds of the acids most often
used in metal finishing. The table can also be reversed to
estimate the acid required to match an alkaline dump.
Because of the variability of this aspect of metal finishing, no
cost figures are given and each reader can use this chart to
figure his own real costs for this portion of waste treatment.
These costs can frequently be associated with disposal of
Table
10
Treatment Cost
1 Gallon
Treatment
Chemical
Sulfuric Acid
2nd stage CN tmt
Sodium Hydroxide
1st stage CN tmt using
Cl:
1st & 2nd stage CN
tmt using Cl:
1st & 2nd stage CN
tmt using NaOCI
Chlorine
1st stage CN tmt
1st & 2nd stage CN tmt
Sodium Hypochlorite
1st stage CN tmt
1st & 2nd stage CN tmt
Cadmium Plating Bath
1st Stage
CNTMT
AMT (Ibs)
—
1 09
—
—
096
—
1 00
1st Stage
CNTMT
Cost
—
$016
—
—
025
—
060
1st & 2nd
Stage
CNTMT
AMT (Ibs)
<001
—
270
028
—
238
—
250
1st & 2nd
Stage
CN TMT
Cost
$001
—
041
004
—
063
—
1 50
Plating
Bath
CuCN
ZnCN
Cd
Table 11
Treatment Costs
1 Gallon Cyanide Plating Bath
1st Stage 1st Stage 2nd Stage
Using Ch Using Using CI2
NaOCI
$0.25 $0.36 $0.63
0.21 0.31 0.54
0.41 0.60 1.05
2nd Stage
Using
NaOCI
$0.94
0.80
1.55
Zinc
Formula
ZnCh
KCL
Boric Acid
Brighteners
Table 12
Bath (Chlorlde)-Make Up
Cone, (oz/gal)
14.0
27.0
4.0
10 ml
Total Cost/Gallon
Cost/Gal
$0.63
1.27
0.11
0.01
$2.02
alkaline cleaners and acid pickles that are unnoticed in most
discussions of waste treatment.
Many shops try to offset the treatment costs by dumping
pickles and cleaners simultaneously. While this practice has
merit, it would be even better if the dumps were not made at
all, or at least on a less frequent basis. Skimming, filtration,
ultra-filtration, and reconstitution of cleaners have all shown
merit in this regard. Electrolytic removal of metals from
pickles has been successful, particularly with easy-to-plate
metals. Theoretically a pickle would last forever if the
dissolved metal could be removed on a continuous basis.
Dragout, of course, requires replenishment and organic
contamination could interfere with surface preparation; but
the individual should consider the merits of this idea (and
others) if acid consumption and related caustic costs are
high.
Ion exchange, in some cases has been cost effective; but
45
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Table 13
Acid Copper Bath-Make Up
Formula CONC Cost/Gal
CuSCv5H:O 28 oz/gal $1 10
HjSCX 7 oz/gal 0 60
Brightener 30 ml 0 06
Total Cost/Gallon $1 76
Table 14
Nickel Bath
Make Up
Formula Cone. Cost/Gal
NiSCv6H:O 35 oz/gal $2.41
NiCI:. 6H;O 10 oz/gal $1 01
Boric Acid 5 5 oz/gal $015
Brightener 40 ml /gal $0.11
Total Cost/Gallon $3 68
Table 15
Theoretical Consumption (Ibs) Of Alkalies For The
Precipitation Of Heavy Metal Per Shift
Heavy Metal To Be Precipitated
Alkali Cu Ni Cr Zn Cd
CafOHh 760 1191 2522 696 316
(Cost) ($023) ($036) ($076) ($021) ($009)
NaOH 456 704 1497 408 184
(Cost) ($068) ($106) ($225) ($061) ($028)
Metal Hydroxide Formation
(Neutralization)
M'!L : + Ca(OH), - M(OH) + CaL
M*V: + NaOH - M(OH); + Na-L
Table 16
Table 17
Theoritcal Consumption (Ibs) Of Alkalies For Th
Neutralization Of 100 Ibs Of Acid
Acid To Be Neutralized
H SO4 HCL
Alkali (Cone) 35% HNO, HF H,BO,
Ca(OH)- 76 36 59 185 180
(Cost) ($2 28) ($1 08) ($1 77) ($5 55) ($5 40)
NaOH 82 39 64 200 194
(Cost) ($1230) ($585) ($960) ($3000) ($2910)
Table 18
Sludge Volume and Disposal Cost Per Shift
At 2% Solids (Wt.)
Type of NaOH Disposal Ca(OH) Dlsposa
Plating TMT (gal) At 0 40/gal TMT (gal) At 0 40/g;
Acid Cu 33.1 $13.24 53.8 $21 52
Cyanide Cu 11.8 4.72 17.0 6.80
Nickel 49.2 19.68 63.8 2552
Chromium 77.0 3080 1109 4436
Acid Zn 30.6 12.24 44.2 1768
Cyanide Zn 102 4.08 14.9 596
Cadmium 10.6 424 154 616
Table 19
Sludge Volume and Disposal Cost Per Shift
At 10% Solids (Wt.)
Type of NaOH Disposal Ca(OH). Disposal
Plating TMT (Ibs) At 0.10/lb TMT (Ibs) At 0.10/lb
Acid Cu 55.4 $5.54 89 4 $8.94
Cyanide Cu 20.0 2.00 28.0 280
Nickel 827 8.27 105.4 1054
Chromium 128.4 12.84 1848 18.48
Acid Zn 51.4 5.14 73.4 7.34
Cyanide Zn 16.7 1.67 25.0 2.50
Cadmium 17.3 1.73 25.4 2.54
Table 16
Treatment Cost Per Shift
At 1 Gallon Per Hour Dragout
Non Cyanide Plating Solution
Type of Treatment Amount
Plating Chemical Ibs.
Acid Copper Sodium Hydroxide 7.44
Nickel Sodium Hydroxide 12.0
Zinc Sodium Hydroxide 8.0
Cost
1.12
1.84
120
regeneration chemicals and associated costs, as well as any
added treatment costs must be considered before leaping to a
conclusion. If the reader is using ion exchange to produce
high purity water for final rinses, printed circuit fabrication
and the like, he should make a careful analysis of
regeneration rates, acid and caustic use, and the waste
treatment cost impact. High volume DI water users are often
surprised or shocked by the true cost figures.
There are some treatment costs that are difficult
establish with scientific precision. These uncertainti
pertain mostly to additives that are pace-fed into the was
stream. Perhaps the most important of these is tl
polyelectrolyte flocculating agents that should be used in i
wastewater systems. The dose rate is normally established c
the basis of flow and amounts to only a few parts per millio
As a consequence of this low application rate, most was
treatment systems require only a few dollars ($l to $5) pi
shift for this material.
Other additives that may be required to achiei
particularly low metal levels, remove fluoride, oils an
grease, detergents and complexing agents, and can also ad
substantially to chemical treatment costs. Here again tr
moral of the story is to minimize the release of the!
substances to the waste streams. For example centrifug;
"chip wringers" can literally pay for themselves by salvagin
46
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Table 20
Sludge Volume and Disposal Cost Per Shift
At 20% Solids (Wt.)
Type of NaOH Disposal Ca(OH) Disposal
Plating TMT (Ibs) At 0.10/lb TMT (Ibs) At 0.10/lb
Acid Cu
Cyanide Cu
Nickel
Chromium
Acid Zn
Cyanide Zn
Cadmium
27.4
10.4
41.4
64.1
25.4
8.8
8.7
$2.74
1.04
4.14
6.41
2.54
0.88
0.87
44.7
14.6
52.7
92.1
36.7
12.7
12.7
$4.47
1.46
5.27
9.21
3.67
1.27
1.27
Sludge
Type of
Plating
Acid Cu
Cyanide Cu
Nickel
Chromium
Acid Zn
Cyanide Zn
Cadmium
Table 21
Volume and Disposal Cost Per Shift
At 30% Solids (Wt.)
NaOH
TMT (Ibs)
18.7
6.7
27.4
42.7
17.3
5.3
6.0
Disposal
At 0.10/lb
$1.87
0.67
2.74
4.27
1.73
0.53
0.60
Ca(OH)2
TMT (Ibs)
30.7
9.3
35.4
61.4
24.7
8.4
8.7
Disposal
At 0.10/lb
$3.07
0.93
3.54
6.14
2.47
0.84
0.87
oil from parts and keeping it from contaminating cleaners
and rinses. Similar attitudes regarding other troublesome
materials can lead to significant savings, reduced operating
costs and less sludge disposal problems.
Now that the chemical costs of wastewater treatment have
been reviewed, we are now in a position to cover the very
important, often troublesome, and usually expensive aspect
to pollution control, namely solids management and
disposal. In some cases suspended metals and metal
hydroxides must be removed from the effluent prior to
release to the sewer or stream. The only exceptions are those
small platers with flows under 10,000 GPD and who have no
lead or cadmium in the discharge. In many locations even
these platers are required by state or local codes to remove
suspended metallics.
At the 10% solids content the sludges resemble toothpaste
in consistency and are usually generated by centrifugjng the
pea-soup sludges of 2 to 5% solids content. It is possible to
approach 20% solids content with small centrifuges
particularly if the heavy metal content is really heavy, as for
example, lead hydroxide. Keep in mind that the centrate or
liquid discharge is not clarified and needs reprocessing (or
repeated recycling). Experience and good engineering as well
as a good centrifuge are required to make a trouble free
installation. If the sludge has a high lime or abrasive content
(from tumble finishing), the bearings, scoops, etc., may
exhibit serious wear. It is therefore incumbent upon the user
or his consultant to "know" his sludge before making a
commitment to purchase any dewatering equipment.
Table 20 shows the effects of 30% solids content on
disposal costs. In the progression from 2% to 30% there has
to be a steady and dramatic reduction in costs, while the
equipment costs have been relatively constant. A small
Sludge
Type of
Plating
Acid Cu
Cyanide Cu
Nickel
Chromium
Acid Zn
Cyanide Zn
Cadmium
Table 22
Volume and Disposal Cost Per Shift
At 40% Solids (Wt.)
NaOH
TMT (Ibs)
14.0
5.5
20.7
32.0
12.7
4.0
4.7
Disposal
At 0.10/lb
$1.40
0.55
2.07
3.20
1.27
0.40
0.47
Ca(OH):
TMT (Ibs)
22.7
7.3
26.7
46.0
18.7
6.0
6.7
Disposal
At 0.10/lb
$2.27
0.73
2.67
4.60
1.87
0.60
0.67
Table 23
Treatment Costs For 8 Mrs At 1 G.P.H.D.O.
(NaOH Used For Neutralization)
Disposal
Plating Make Up Treat Cost Total
Bath Cost Cost At 30% Cost
Cu
CuCN
Ni
Cr
Zn
ZnCN
Cd
$14.08
11.92
29.44
18.80
16.16
8.16
8.88
$1 12
7.87
1.84
3.61
1.20
7.31
12.86
Solids
$1.87
0.67
2.74
4.27
1.73
0.53
0.60
$17.07
20.46
34.02
26.68
19.09
16.00
22.34
100 psi, recessed plate, pressure filter can be purchased for a
little more than a comparable centrifuge, and probably for
less than a vacuum filter. Here again a semi-granular sludge
can be dewatered more efficiently and actually produce solids
levels of 35% or better. Of course the filter must be sized to
match the sludge accumulation rate, and large filters can be
quite expensive. Automation and safety features such as
light curtains, interlocks etc., can raise the prices further.
Care must be exercised in pressure filter selection to assure a
proper match to a particular situation.
High pressure filtration using recessed plate filters with
200 psi or higher feed pressures will produce even drier
sludges, usually in the range of 35 to 50% solids.
Table 22 shows how these filters could effect disposal
costs. While these filters are more expensive than the lower
pressure types, high accumulation rates and/ or long distance
disposal could easily justify the added expense.
Table 23 presents a consolidated overview of wastewater
treatment costs from the initial investment in the plating
bath make-up through final sludge disposal of a nominal 30%
solids content. Notice that this paper has not considered
waste treatment systems costs, depreciation factors, operator
salaries, power requirements (costs), maintenance costs and
the like. Obviously the figures will relate to the size and
complexity of the effluent treatment system and impact
upon the figures presented here. If the reader takes the time
to add these costs to the ones presented he will obtain a true,
bottom line for the cost of wastewater treatment, and
perhaps generate sufficient motivation to initiate
conservation and/or recovery programs.
The technology of suspended solids removal is well
documented and covers a variety of methods ranging from
circular clarifiers and rectangular settling tanks to tube and
47
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lamella settlers. Regardless of the technology and equipment
employed, the common factor is the sludge produced while
clarifying the effluent. Without special thickening devices the
sludge produced will range from 0.5 to 2% solids; but with
thickening, the solids content could be as high as 5 to 7%.
Table 18 shows the sludge volume and disposal costs at 2%
solids for a single eight hour shift using the one gallon per
hour drag-out rates previously developed. It is readily seen
that these costs with sodium hydroxide use are very high and
with the use of lime are further elevated. The fact that lime is
seldom as efficient as theory would predict results from its
limited solubility and its deactivation by fluorides, sulfates,
oils and grease. Lime must therefore be applied in excess of
theory and increased sludge volumes result. It is important to
consider this factor, as well as initial cost, whenever
contemplating the use of lime in wastewater treatment.
The cost of diposal of sludges at the two percent solids
concentration will obviously be unacceptable to all but very
small generators with low sludge accumulation rates. For
those with higher generation rates, compaction of some sort
must be employed. There are a variety of dewatering
methods available to the finisher and each application must
be judged on a case-by-case basis. The cost of the dewatering
equipment, operating costs, maintenance, and anticipated
disposal costs based upon expected generation rates at any
given solids content must be considered in the selection
process. It would be wise to check with local haulers and
disposal sites concerning any limitations with respect to
solids (or moisture) content. In some places sludges with less
than 25% (or 30, or 35%) solids are not acceptable. It would
be an unfortunate error to select a dewatering device that
could not produce a proper solids content for the disposal
location selected.
The effects of raising the solids content to only 10% are
shown in Table 19. There is an obvious and dramatic
reduction in disposal cost. If the reader's costs do not
correspond with those presented, it would not be difficult to
adjust the figures to correspond to local conditions. The ten
cents per pound may be somewhat high for the present. A
survey of actual costs showed that many haulers charge by
the pound or ton, then add a mileage and disposal fee for
each load. In a number of cases the combined cost came to
about 7.5 cents per pound ($150.00 per ton), as compared to
quotes of 60 to 100 dollars per ton, without mention of the
"extras". The haulers also indicated that their prices would
go up as fewer disposal sites were available, and hauling
distances increased. On this basis, 10 cents per pound makes,
an easy figure to work with, while not being entirely
unrealistic.
The work described in this paper was not funded by the U. S.
Environmental Protection Agency and therefore the contents
do not necessarily reflect the views of the Agency and no
official endorsement should be inferred.
48
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Energy, Environmental and Safety Benefits Through
Computer Controlled Curing Oven Processes
Wilbur F. Chinery and Stephen J. Ansuini*
INTRODUCTION
It is not often we set out to reduce energy costs and
achieve it along with higher air quality being exhausted to
the atmosphere. These items though most often inversely
proportional have proven to be the exceptions rather than
the rule in this project. This project came about as a
cooperative effort between private industry and the U.S.
Government. The Environmental Protection Agency's
Industrial Environmental Research Laboratory along with
the Department of Energy's Office of Industrial Programs
worked with the Chemical Coalers Association; Centec
Corporation's Process System Group, an engineering firm
applying microcomputer technology to the manufacturing
industries with offices based in Ft. Lauderdale, Fla.; and
Mack Trucks, Inc., a manufacturer of heavy duty trucks
with offices based in Allentown, PA.
The demonstration was carried out in our Small Parts
Paint Building (SPPB) at our Allentown Assembly Plant.
The building, 106,500 sq. ft., contains four separate paint
systems, an eight stage zinc phosphate washer, four
elevated ovens and the necessary supporting equipment.
Figure 1 shows the functional diagram of the SPPB's four
ovens and incinerator operation. The color and prime ovens
are spray paint ovens where parts receive one of three
modes of paint application: conventional spray, airless
spray, or electrostatic spray. The color, prime and dip oven
(CPD) exhausts are combined at the CPD exhaust fan then
passed through an auxiliary heating coil and sent to the
catalytic incinerator for Volatile Organic Compound
(VOC) destruction. After passing through the catalytic bed
the gases can pass through or by-pass an air-to-air heat
exchanger, which provides the necessary heat for the fourth
oven, operating at 350° F. This is the only heat source for
the electrodeposition ("E"-Coat) curing oven.
BENEFITS
Oven air-flow control technology extends to us several
benefits:
Environmental
—Utilizes recovered heat effectively
—Assures 90% destruction efficiency
Energy
—Reduces operating costs of ovens
—Reduces operating costs for incinerator
control equipment by 10 to 55%
—20% investment tax credit (at time of writing)
Other
—Safer operation by several orders of magnitude
* W F. Chinery, Manager Facilities Dept
S. J Ansuini, Facilities Engineer
Mack Trucks, Inc
Allentown, PA
than uncontrolled systems
-Expandable to 3-oven and
control
one incinerator
ECONOMICS
"The curing processes are energy intensive and usually
account for more than 50% of the total manufacturing
energy. Significant energy losses occur because of venting
from the curing ovens"1 caused by high dilution air flows.
The payback period and the investment amount would be
highly dependent on air flow rates, solvent removal rates
and system configuration. However the Discounted Cash
Flow (DCF) rate of return and payback have shown
'DOE Tech. Briefing Report, "Oven Curing- Energy and Emission Control in Coil
Coating," TID-28705, 1978.
E-COAT
OVCN
DIP
OVCN
J«0*t
LCL CWH I HQL1.BB
I EXHAUST DAMPER
u—"ays*—d
CONSTANT VOLINH
INCINERATOR HEAT
EXCHANGER SUPPLIES
ALL HEAT FOR
E-COAT OVEN
Fig. 1—Functional diagram of SPPB 4 Ovens and Incerator System.
Fig. 2—Control System Operation Flow.
49
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FID BURNER
1/2' LINES FROM SAMPLE PROBES
Fig. 3—Typical Fid Analyzer Detection Unit Flow Diagram.
Fig. 6—Self-Cleaning Prefilter Station.
Fig. 4—Overhead View with Sample Points Indicated.
Fig. 5—Equipment Room SPPB Mack Trucks, Inc.
favorable figures when dealing with paper, fabric, wire, coil
and other coalers involving high air flow rates.
We at Mack are working with one oven with a low flow
rate, 3400 scfm, and have successfully reduced it by 85%.
The dip oven exhaust now measures 400 to 500 scfm. With
this reduction of cooler dilution air we have cut previously
required Btu's to maintain oven temperature substantially
It is estimated conservatively we are realizing a $26,000
annual savings on fuel. The reduced air flows would allow
for incinerator down-sizing providing still another savings.
COMPUTER CONTROL SYSTEM
Purpose: Automatic and continuous control of the
dilution air flow into the curing oven and other tasks like
monitoring and logging essential information are just a few
of the computer's duties.
We began by sketching a control system operational flow
diagram. It was imperative that we observed strict safety
parameters at this point. The system should be capable of
detecting: computer failures, high caution levels, high alarm
levels, analyzer failures and power interruptions. Once the
failure is detected, the system should act with fail safe
precision. To achieve this the "what if and the fault tree
analysis were utilized. Figure 2 shows a basic control
system. In addition to the Lower Explosive Limit (LEL)
Analyzer (AIT- ) and micro-computer hardware, the
dilution air-flow control system includes temperature
(TCV- ), and pressure (PT- ), automatic dampers with
pneumatic actuators (FCV- ) and actuator controls (I / P).
The I/ P units take an electrical signal from the computer,
interpret it, and provide a proportional pneumatic pressure
to the actuator.
Safe operation of the system is dependent on the
sensitivity, reliability, and stability of the VOC vapor/LEL
Analyzer. A multi-point Flame lonization Detector (FID)
Analyzer was selected for the control system. Figure 3 is a
typical FID Analyzer Detection Unit flow diagram. The
FID burner receives hydrogen gas as its fuel, combustion
air and the sample gas. Prior to injection, air is added to the
sample gas to ensure complete combustion of the sample.
Within the FID burner are two plates separated by the
combustion area. One plate is at a 200v potential and the
other is the signal input to a high gain amplifier. As the
sample gas is burned it allows the signal plate to pick-up a
signal which is directly proportional to the amount of
VOC's present. Other controls allow the introduction of
zero gas and sample gas for calibration needs.
The control room location was also a point of
consideration. It was necessary to minimize the sample line
runs outside the oven which required heated lines and to be
centrally located for the color, prime, dip ovens and the
incinerator. For this reason it was positioned below the
incinerator exhaust stack as indicated in Figure 4 by the
dotted line around sample point "G". A 10 ft * 12 ft modular
50
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Analyzer, AIT-1:
A Primary D.O. Air Seal
B D.O. Exhaust
C D.O. Zone 1
D D.O. Zone 2
E Fume Tunnel Exhaust
E Fume Tunnel Exit
E1 Fume Tunnel Auxiliary
F2 CPD Combined /Incin. Inlet
G Incin. Exhaust
H Ambient
Analyzer, AIT-2.
W P O. Product Inlet
X P.O. Exhaust
Y C.O Product Inlet
Z C.O. Exhaust
DO— Dip-Coat Oven P O.
Metal
Prefilter
Yes
Yes
Yes
Yes
No
No
No
Yes
Yes
No
Yes
Yes
Yes
Yes
— Prime Oven C O
Table 1
Bypass Type
Yes
Yes
Yes
Yes
No
No
No
No
No
No
Yes
Yes
Yes
Yes
— Color Oven
Process
Temp.
250° F
250° F
250° F
250° F
85° F
85-220° F
85-220° F
220° F
600° F
85° F
250° F
250° F
250° F
250° F
Heated
Line
Yes
Yes
Yes
Yes
No
No
No
Yes
Yes
No
Yes
Yes
Yes
Yes
enclosure proved neessary as indicated by Figure 5. Item
one is a four channel FID Analyzer (Ratfisch), two - an
Omni-800 printer (Texas Instrument), three - color video
terminal (ICS), four - 8,000 parts per million (ppm)
methane in nitrogen calibration gas, five - a Mark V
hydrogen generator 300 ml/min. (Milton Roy), six - the
cabinet houses the heart of the control system an Intel 8080
microprocessor and interfacing hardware, seven - an eight
channel FID Analyzer (Ratfisch).
The video display gives necessary data to the viewer and
includes the date and time, percent LEL for eight sample
points and a normal/failure indication on four other LEL
points in the color and prime spray ovens; temperature
information and pressure information on the dip oven;
temperature levels in the fume tunnel, incineration inlet,
pre-catalyst and post-catalyst; destruct efficiency and
percent open of the dip inlet and exhaust dampers; alarm
horn enable switch on/off; and whether the system is in a
monitor mode or control mode (auto). The bottom of the
screen provides information to the inquirer as to those items
that may be accessed. By knowing a password the operator
can make some control level changes as long as they fall
within the pre-programmed limits. A graphical display may
also be employed at the discretion of management.
Figure 4 shows sample point locations as originally
proposed and how they were installed. As this was the first
system of its kind in the world, we exercised extreme
caution and sampled more points than we now feel were
necessary for our particular application. Table 1 shows a
breakdown of the sample points indicating four parameters
of importance. The heated sample lines are necessary to
maintain sample integrity by preventing condensation from
occurring in the lines. They are adjusted at the FID
Analyzer to the oven operating temperature and controlled
thereafter by the Ratfisch electronics package. Each
sampling probe was locally fabricated at a substantial
savings over purchasing manufactured ones. A length of
stainless steel Vi in. or !4 in., dependent on type, was capped
and a series of small holes were equally spaced across the
duct opening. The number of holes were calculated to allow
the same flow as the tube size. All sample lines that were
routed through a self-cleaning prefilter station, shown in
Figure 6, were run using half inch stainless tubes to the filter
and a '/4 in. was then fed from each filter to the oven floor
where transition was made to a heated sample line.
Figure 6 shows the self-cleaning prefilter station. The
draw on the four filters is provided by an air eductor
(ejector). Supply instrument air is at 35 psi and each filter
has a flow of 2 cfm. The analyzer pump pulls only 5,000
ml/ min from each filter line, and of that only 20 ml/min is
used by the FID for analysis. This method of sampling
provides minimum reaction time to LEL changes within the
oven. In our application this is not as critical, as we are
looking at a 30 minute residence time of our parts, but
would be critical for a coil coater working with seconds for
residence time.
CONCLUSION
The potential benefits of this control technology have
long been under investigation. For the miscellaneous metal
products coating industry alone, fuel savings would be
substantial. Product lines in this industry include office
furniture, major and small appliances, industrial cabinets
and partitions, toys, kitchen utensils, lawn furniture and
other small metal products.
There are approximately 6,000 of these ovens in
operation in one thousand plants across the country. If this
control technology were applied to 10% of the ovens
mentioned above, the 600 ovens have a potential annual
savings equivalent to 1.5 million barrels of oil. If each of
these ovens had an incinerator for VOC control the annual
savings would increase to 6.8 million barrels of oil.
It is important to look at the LEL levels at the reduced air
flows. As we discovered it may not always be necessary to
have a controlled system even when reducing air flows 85%.
A continual monitor with alarm levels may save a great deal
of front end costs. The initial field surveys are critical and
more attention should be given to this important
foundation.
This paper has been reviewed in accordance with the U. S.
Environmental Protection Agency's peer and
administrative review policies and approved for presenta-
tion and publication.
51
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Oily Wastewater Treatment By
Electrochemical Techniques
Delia M. Yarema*
This paper will discuss The Stanley Works proposed
project to treat oily wastewater by an electrochemical
technique patented by the Ford Motor Company. The
reasons for the selection of this method and the anticipated
benefits will be featured.
The Stanley Works is a major manufacturer of builders
hardware, hand tools and fabricated metal products. I am
sure you will all recognize our Corporate slogan -
STANLEY HELPS YOU DO THINGS RIGHT. In
environmental areas, Stanley shares the feeling of all metal
finishing industries represented here today in trying to do
things right with respect to pollution abatement. However,
finding economically attractive technologies that can be
practically applied on a day-to-day basis is a constant
problem.
The Stanley Works Corporate Headquarters is located in
New Britain, Connecticut. Within this complex are many
Stanley divisions and Corporate support groups.
Wastewater generated from manufacturing operations is
discharged to twenty-six separate sanitary sewer
connections. To insure compliance with State and local
discharge regulations, an intensive wastewater discharge
assessment program was conducted in 1979. This survey
identified oil/grease discharges requiring additional
treatment to bring them within the Publicly Owned
Treatment Works (POTW) limit of 100 mg/1. One of the
systems identified as a problem area was the discharge from
an American Petroleum Institute (API) separator within
the Hardware Division.
The API separator accepts a maximum of 45,000 gpd of
oily wastewater from industrial washers located in Building
150. Manufacturing operations include rolling, broaching,
tapping, drilling, counterboring and stamping. Before parts
are stored, plated, or painted, residual oil, dirt, and metal
chips are removed in the industrial washing machines. In
some cases, parts must be washed between successive
manufacturing operations. Since the metalworking
operations require lubricants with diverse properties, the
oils used range from chlorinated compounds to heavily
pigmented materials. This complex waste stream flows to
the API separator where free oil is removed. However, the
resulting wastewater discharge still contains approximately
1000 mg/1 of emulsified oil.
A combined task force of Corporate facilities engineering,
Corporate laboratory, and manufacturing personnel re-
Oelia M.. Yarema
The Stanley Works
New Britain, CT
viewed the entire operation to assess the extent of the prob
lem. Guidelines were established to streamline the numbe:
of lubricants presently in use. This is still an ongoing procesi
since a change in lubrication must be carefully evaluatec
with respect to lubricity, tool and die life, ease in cleaning
and protection against rust in storage. Wherever possible
flow restrictors and solenoid valves are utilized to reducx
the volume of water. The use of cleaners that split out oi
have reduced the load on the API separator. However, aftei
all these modifications the waste stream requires treatmenl
prior to discharge to the sewer.
In determining the method of treatment to be used foi
this waste stream some basic factors were extremely
important.
1. We needed to produce treated water of a quality thai
would be both acceptable for discharge to the sanitary
sewer and for future re-use as make-up water for the
industrial washers. With proposed sewer taxes and the
probability of future water shortages, the
continuation of draining to sewer was at best a
temporary solution.
2. The treatment method must handle a waste stream
variable in oil concentration, surfactant level, and
paniculate contamination with reliable results.
3. The system must be fully automated and require a
minimum of operator attention.
4. The system must be cost effective with respect to
capital and operating expense.
Initially, the following processes were considered for the
removal of emulsified oil from this waste stream:
1. Conventional Chemical Treatment,
2. Colloid Piepho System RP,
3. Ultrafiltration, and
4. High Speed Centrifuge.
Conventional Chemical Treatment utilizes acid and
inorganic chemicals to break the emulsion. If we chose to
pursue this treatment method, we would have to abandon
our idea of re-using the water unless a demineralizer was
placed on the return water line. Acid and inorganic
chemicals would allow the continual build-up of dissolved
solids which could result in corrosion problems with
product going to storage. Conventional treatment is best
suited to a batch type operation as opposed to continuous
treatment and normally it requires intensive floor space.
Chemical treatment costs would be approximately
85
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to review alternative methods for treating the oily
wastewater with conventional treatment as a last resort.
A plant trial was conducted utilizing a Colloid Piepho
System RP. Colloid Piepho supplies a proprietary multi-
functional chemical to be used with their equipment. This
chemical is a clay type material which appears to sorb the
emulsified oil. The resultant sludge is dewatered utilizing a
moving paper filter. Although effluent oil analyses were less
than 25 mg/1, the inherent operating costs of the system
proved unacceptable. Chemical costs were estimated to
range between $25,000 and $50,000 per year with a capital
cost for an automated system at $75,000. Additional costs
would include the paper for the filter and transportation
and handling charges for removal of the sludge from the
plant property. Since solid waste landfills in Connecticut
are approaching capacity levels, we could be building into
the system an escalating disposal cost.
A third option for treatment of the emulsified wastewater
was Ultrafiltration. Ultrafiltration is a low pressure
membrane process to separate the emulsified oil from the
wastewater. As the wastewater flows across the membrane,
water and low molecular weight materials pass through the
membrane and are collected as permeate. Emulsified oil
and particulate matter are retained by the membrane. In
this way the oil can be concentrated to between 50-60%.
Performance of the system is optimized by the removal of
free oil and readily settleable solids. Membrane flux (gfd of
permeate) can be affected by temperature, concentration of
free oil in the wastewater, and the fouling rate of the
membrane. Laboratory experimentation indicated that
some of the surfactants involved in either the basic
formulation of the lubricant or cleaning chemicals can pass
the membrane. These materials would then recirculate and
concentrate within a re-use water system. Basic capital cost
for the ultrafiltration system was $ 175,000. We were aware
that replacement membrane cost could run as high as 25%
of the capital cost every four to five years.
Brief Laboratory studies indicated that a High Speed
Centrifuge (13,000 g's) was not effective in breaking the
emulsion. This treatment concept was therefore
abandoned.
In our review of the available treatment methods, it
became apparent that no one system would satisfy all of our
needs in a cost effective manner. Through the EPA
Research Laboratory in Cincinnati, we learned of a process
developed by the Ford Motor Company which treats oily
wastewater by electrochemical means. Ford held patents on
the process and had developed a 1500 gpd pilot unit at their
Lavonia, Michigan Transmission Plant. The pilot unit was
treating oily wastewater from diverse machining operations
similar in nature to those done within the Hardware
Division of The Stanley Works. The wastewater contained
emulsified oils, surfactants, and tramp oils as well as
occasionally being contaminated with hydraulic oils,
drawing compounds and transmission fluids. As with the
waste stream in our plant, Ford's waste stream changed
frequently in composition. However, initial results
published by Ford indicated that they were able to treat oily
wastewater containing from 300 to 7000 mg/1 of oil/grease
to less than 50 mg/1 in 90% of their trial work. This
treatment level is well below the 100 mg/1 discharge limit to
our sanitary sewer and would be totally acceptable for re-
use water characteristics.
Our initial contacts with the EPA and the Ford Motor
Company generated extreme interest on the part of The
Stanley Works to obtain more information about this
system. The Ford Motor Company granted The Stanley
Works a limited patent license to operate a treatment
system within the New Britain Complex of The Stanley
Works. Preliminary feasibility studies conducted in our
Laboratory allowed us to reduce the oil content in our
discharge by 99%.
The Ford System is a continuous process which employs
a porous electrode that can be operated at a low voltage and
low current to yield essentially oil-free water. Oily emulsion
wastewater is collected in a flow equalization tank where
free floating tramp oil can be removed utilizing a skimming
device. The waste stream requires sufficient conductivity for
cell operation and to prevent passivation of the iron
electrode. In the Ford System, calcium chloride is added to
the waste stream prior to entering the electrolytic cell. The
cell is comprised of a caged bed of iron or steel machining
chips which act as an anode with a perforated steel metal
sheet as a cathode. Voltage is applied to the electrodes,
dissolving ferrous ions at the anode and forming hydrogen
and hydroxyl ions at the cathode. The ferrous ions react
with the chemical oil-emulsifying agents, and with the
addition of air are oxidized to ferric ions, further
destabilizing the emulsion. The destabilized oil emulsion
droplets sorb onto the dispersed and reactive ferric
hydroxide floe. An oil-rich sludge is generated. In the Ford
System, flotation is assisted by the introduction of micro-
bubbles into the cell flotation section. A belt skimmer
collects the sludge blanket while clear water overflows to a
sand filter and then to a clean water tank.
Ford's research has shown that the oil content in the
effluent has a direct relationship to turbidity. The system
has been automated so that the signal from a turbidimeter
controls the applied current. Ford's system normally
operates at an average voltage of 20 with current ranging
from 15-35 amps.
Stanley's proposed project would utilize a dissolved air
flotation unit for sludge collection rather than an air
bubbler flotation system. We do not anticipate the need for
final polishing of the effluent and therefore would not
employ a sand filter at this time.
Economic projections are favorable with an anticipated
capital cost of $60,000. The major portion of this
expenditure would be for a commercially available
Dissolved Air Flotation (DAF) unit. Machining chips are
readily available within the New Britain Complex as an iron
source. The exact amount of chemical required for ionic
conductivity still needs to be determined. We will
investigate the possibility of utilizing a material that would
not only increase the conductivity but also provide a
corrosion inhibiting property to the water.
Operating cost is directly related to flow rate, current and
type, and concentration of chemical. For a given influent
composition and flow rate, the current determines the rate
of iron dissolution and therefore the ratio of iron to oil. To
operate the system at a minimum cost, this ratio must be
kept as low as possible without sacrificing effluent oil
quality. Work completed by Ford was directed towards
obtaining an effluent oil concentration in the range of 10
mg/1.
Since we would not require this level of water quality, we
anticipate our operating costs to be lower than the 68e/1000
gallons that Ford has reported.
In our opinion, the practical demonstration of this
process on a larger scale than Ford's 1500 gpd pilot unit is
extremely important to the metal finishing industry. The
electrochemical treatment method would allow for the re-
use of the water, generate a minimal quantity of sludge rich
in oil, while utilizing an available waste material (scrap
53
-------
steel) in the treatment process. We feel that this system is the
best technology available for the resolution of our oily
wastewater problem.
1 would like to take this opportunity to thank the Ford
Motor Company for their continued assistance in this
project, particularly Dr. Marvin Weintraub for providing
the slides of the electrochemical process utilized in this
presentation.
We look forward to reporting to you at a later date the
results of our project.
REFERENCES
1. Gealer, R. L., Golovoy, A., Weintraub, M., "Electrolytic
Treatment of Oily Wastewater from Manufacturing and
Machining Plants," June 1980, Report No. EPA-600/2-
80-143.
2. Weintraub, M. H. Gealer, R. L., "Development of
Electrolytic Treatment of Oily Wastewater," Report
Presented at American Institute of Chemical Engineers
1977.
The work described in this paper was not funded by the U. S.
Environmental Protection Agency and therefore the contents
do not necessarily reflect the views of the Agency and no
official endorsement should be inferred.
54
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Cross Flow Filtration Technology
For Metal Finishers
Han Lieh Liu and James Blacklidge*
INTRODUCTION
This paper presents the results of two wastewater
treatment technology evaluation programs sponsored by the
U.S. Environmental Protection Agency (U.S. EPA). These
programs were concerned with the application of a
microfiltration system designed to treat industrial wastes
containing heavy metals. Major results of the first program,
a lead-acid battery manufacturing wastewater study, have
been published ("Removal of Heavy Metals and Suspended
Solids from Battery Wastewaters: Application of
Hydroperm Cross-Flow Microfiltration" EPA^OO/S2-81-
147). Additional data from the first program are provided in
this paper. The second program concerned the use of a
microfiltration system to treat electroplating wastewaters.
The results from that study are the main subject of this
presentation.
Conventional wastewater treatment technologies for the
electroplating industry consist of physical and chemical
processes for the destruction of cyanide, the reduction of
hexavalent chromium to the trivalent state, and the
neutralization/precipitation/clarification of heavy metals in
wastewaters. Heavy metals are usally precipitated as their
hydroxides. These metal hydroxides usually have low
solubility and can be precipitated by adjusting the pH to an
appropriate level; however, because some of these metals are
amphoteric, the precipitation of these metals is not an easy
task in the treatment of plating wastewaters.
The separation of precipitated solids has been a challenge
to the metal finishing industry. Traditional separation
techniques, such as gravity settling and centrifugation, are
not totally effective since the precipitated solids are usually
hydrous and have densities very close to that of water. In
addition, the design of the required clarifier, in a number of
instances, limits the retention time in the settling chamber
due to size limitations. There is, therefore, a need to develop
more compact alternative solid/liquid separation techniques
for treating electroplating wastewaters.
In recent years, the use of cross-flow filtration has been
broadly employed in various solid/liquid separation
applications. In this process, the direction of the influent
flow is parallel to the filter surface, while filtrate permeation
occurs in a direction perpendicular to the flow. Examples of
cross-flow filtration include membrane filtration techniques
such as certain types of ultrafiltration (UF) and reverse
osmosis (RO). The major disadvantages of membrane
filtration systems include high energy consumption rates and
low filtrate fluxes. The cross-flow microfiltration system,
*Han Lieh Liu
Hydronautics, Incorporated
Laurel, Maryland
James Blacklidge
Craftsman Plating and Tinning Company
Chicago, Illinois
developed by Hydronautics under the registered name
HYDROPERM®, shows the capability of removing
suspended solids from wastewater with relatively low
filtration pressure (1 kg/cm2, 15 psi) while maintaining a
reasonably high filtration rate.
As indicated, this paper presents the results of two field
investigations ultilizing microfiltration (MF) in both an
electroplating shop and a battery manufacturing plant. A
general description of the cross-flow microfiltration
technology is presented first. Field evaluation results are
then presented.
Cross Flow-Microfiltration
In this process, a quasi-steady state operation is possible,
since the continuous buildup of the separated solids on the
filter surface is largely prevented by the hydrodynamic shear
exerted by the circulation flow.
There are some fundamental differences in UF and RO
systems and the microfiltration system. J. D. Henry, Jr.
suggested1 that microfiltration involves the retention of un-
dissolved (particulate) material by the filtration barrier with
tangential suspended flow while UF and RO involve the
retention of dissolved species by the filtration barrier with
tangential solution flow. In practice, this difference generally
results in much higher filtration rates (flux) and lower energy
requirements for microfiltration than for UF and RO.
Other significant physical and operational differences
between UF, RO, and MF include filtration barrier wall
thickness, pore size, liquid circulation velocity, and
operating pressures. The typical UF and RO wall thickness is
usually a few microns, whereas the MF wall thickness is
approximately one millimeter. The pore size of UF and RO
are less than one micron while MF pores are in the range of
two to ten microns. The UF and RO liquid circulation rates
are greater than 6 m/sec (20 ft/sec) while MF requires less
than 2 m/ sec (7 ft/ sec). Finally, RO operates in the range of
42 to 84 kg/cm2 (600-1200 psi) and UF operates in the range
of 3.5 to 11 kg/cm2 (50-150 psi). MF is usually operated at
less than 1.4 kg/ cm2 (20 psi). The higher operational circula-
tion velocities and pressures used for UF and RO systems are
the results of the separation mechanisms involved.
In UF or RO, the fluxes are determined by a balance
between convection of dissolved species proportional to the
flux itself and back diffusion due essentially to molecular
processes. This is true whether the tangential flow is laminar
or turbulent. As the flux increases, the wall concentration
due to polarization of filtered species increases (more rapidly
for species of lesser diffusivity) until gelatin finally occurs.
Thereafter, the gel layer grows until convection is balanced
by back diffusion which is temperature dependent. As a
consequence of the above process, during ultrafiltration the
equilibrium flux is independent of filtration pressure beyond
a certain pressure, and increases as the molecular diffusivity
and wall shear (i.e., circulation velocity) increase.
In microfiltration, the fluxes are determined by
55
-------
Table
1
Permeate Quality During the Field Demonstration at CPT
Date
5-28
Sample 1
Sample 2
5-29
6-1
6-5
Sample 1
Sample 2
6-8
6-10
6-15
6-15
6-19
6-29
6-30
7-6
7-7
7-12
7-21
Sample
ID
C*
PI
Fl
P2
F2
S
P
F
S
PI
Fl
P2
F2
P
F
C
PI
Fl
P2
F2
PI
Fl
P2
F2
PI
Fl
P2
S
S
P
F
S
S
P
F
*Taken after setting overnight from
C = Clanfier; P
= Permeate; F =
pH
10.44
11.25
11.29
10.54
10.44
10.66
10.30
10.28
9.91
9.60
9.47
9.86
9.51
7.82
7.55
12.37
7.25
7.14
6.11
6.39
9.60
9.52
9.59
953
11.4
10.8
10.5
10.4
937
1048
10.98
10.68
9.93
9.95
9.88
TS
mg/l
4030
4580
4960
2330
7810
12470
5090
12020
31450
4080
4750
1900
11740
2620
10890
4400
8420
12550
5730
20000
6780
13230
5840
25640
9677
8700
6680
12700
16000
14240
26450
11120
12920
1290
3940
TSS
mg/l
2.0
6.0
408.0
8.0
5530.0
8796.0
6.0
5940.0
25280.0
<0.1
4540.0
<0.1
9710.0
<0.1
8480.0
42.0
65.3
3610.0
217.0
14390.0
16.0
6570.0
4.0
17490.0
14.0
1240.0
7.0
7500.0
14430.0
7.0
12310.0
7160.0
8780.0
1.5
2530.0
Cd
mg/l
0.4
0.1
44.0
0.3
1100.0
2000.0
0.2
1200.0
7000.0
0.4
700.0
0.4
1600.0
0.9
380.0
7.1
132.0
4600
165
810
0.4
1200.0
0.3
3200.0
0.1
250.0
0.1
1350.0
-
1.7
-
-
-
0.1
-
Cu
mg/l
0.1
0 1
1.5
0.1
24.0
51.0
<.i
22.0
106.0
1.4
23.0
4.5
37.0
0.3
33.0
0.5
3.8
17.5
3.6
44.0
0.3
100.0
0.9
310.0
02
11.7
0.1
50.0
-
0.3
-
-
-
0.9
-
Zn CNT
mg/l mg/l
O.I
<.l 17.1
7.6
<.l
130.0
280.0
<.l 21.5
190.0
720.0
<.l 10.1
120.0
<.l 3.0
240.0
<.I
57.0
0.9
0.3 0.6
22.0
0.4
67.0
<.l
100.0
<.I
260.0
0.1
30.0
0.1
110.0
-
0.1
-
-
-
0.2
-
CrT
mg/l
37.2
29.7
35.2
28.0
<.l
-
-
<.l
-
<.l
-
-
-
-
-
-
-
-
-
-
-
supernatant of clarifier.
Feed; S = Sludge
in the microfiltration recirculation tank (C is
taken from supernatant
of clarifier).
convection of particles (rather than dissolved species)
proportional to the flux and the phenomenon which
removes particles from the gel layer. With all environmental
conditions being equal for comparative purposes, the cross-
flow microfiltration of particles results in significantly larger
fluxes than those noted during ultrafiltration of the dissolved
species even though dissolved species have larger
diffusivities.
Recently this solid removal mechanism in cross-flow
filtration was reexamined by Tulin.2 An erosion and
deposition model was proposed. The model is analogous to
the erodibility of sediment on the river bottom through the
action of tangential flows (currents and waves). It is known
that sedimentary materials are picked up from the river
bottom when the tangential shear due to flow exceeds a
threshold value. The material is subsequently carried in the
direction of the current for a certain distance before being
redeposited. Eventually, changes in the concentration of
sediment in suspension reflect the net difference between
rates of entrainment and deposition. The threshold value of
shear stress, however, is dependent on the exact physical and
chemical nature of the sediment (i.e. cohesiveness). The same
types of erosion and deposition model can be applied to the
cross-flow microfiltration system by adopting an additional
variable, the permeation velocity. This mathematical mode.
is still under investigation at this time.
The microfiltration technology results in a self-contained
effluent clarification system that does not require the space.
liquid flow, or retention time associated with typical
clarification systems. The system used in these evaluations
required a fraction of the space that normal clarification
systems require to process the same effluent volume.
Field Evaluation
The microfiltration system filters used in the electroplating
evaluation program were supplied by Hydronautics,
Incorporated under the registered name, HYDROPERM®.
The principal element of the system is a thick-walled (1 mm,
0.04 in), hollow tubular filter (6 mm ID, 0.24 in) made of
thermoplastic material and containing micron-size pores.
The module, which was constructed for the full-scale
system, contains eighty filter tubes in a 1.5 m (5 ft) long, 100
mm (4 in) diameter PVC pipe. The filtration surface area of
one such module is 2.3 m (25 ft2). Four such modules, with
a total surface area of 9.2 m2 (100 ft2) were arranged in
parallel and in series on a skid base. Also mounted on this
base were the feed circulation pump, permeate transfer
pump, permeate holding tank, and clean solution tank. A 3.7
56
-------
kW (5 hp) pump with a capacity of 681 1pm at 18 m head
(180 gpm at 60 ft) was used to circulate the feed through the
module system. The total system is pictured in Figure 1. This
system is entirely self-contained. The only requirements for
interfacing to the plating shop are the power line connection
and feed line connection to the recirculation tank.
The Craftsman Plating and Tinning (CP&T) Corporation
in Chicago was selected as the evaluation site for
electroplating wastewaters. The plating processes are either
barrel or rack. Metals plated are cadmium, copper, tin, tin-
lead, and zinc. Special treatment in the shop include
chromate conversion coating, etching, passivating pickling,
hot solder dipping, and organic coating. The wastewaters
(from dragout, rinse, spill, cleaning, etc.) flow to a common
sump at a rate of about 7570 1/hr (2000 gal/hr). CP&T
treats its wastewater with conventional processes including:
cyanide destruction by chlorination; neutralization with
caustic, suspended solids removal through clarification, and
sludge thickening by centrifugation. The treated water goes
to the city sewer. The flow diagram for the plant wastewater
is shown in Figure 2. The microfiltration system was
connected to the existing treatment facility at the
neutralization tank discharge line. It was operated in parallel
with the clarifier unit. A comparison of these two unit
processes was therefore possible.
During the eight-week evaluation period, data were taken
to determine permeate flux rates and permeate quality. The
permeate samples were taken weekly and analyzed once per
week by Scientific Control Laboratory, Incorporated,
Chicago.
The feed to the microfiltration unit was the actual
wastewater flow from the plant. It experienced a daily
variation due to the type of plating conducted during the
day. The associated pretreatment steps, cyanide destruction
and neutralization, were adjusted accordingly. There were
periods however, when the pH and cyanide destruction
processes were not adequately controlled. During those
times both the M F and the clarifier processes showed poor
effluent quality. This result, however, was anticipated since
the capability of both processes, MF or clarification, is
dependent upon the success of the initial pretreatment steps.
Table 1 shows the microfiltration system performance
during the field evaluation. Initial daily flux values were
much higher than the corresponding plateau values, (i.e.
steady state operating values) typically in the range over
24,450 l/m2/day (600 gal/ft2/day). The rate of decay of the
flux values to plateau values during the day depends on feed
wastewater characteristics. This in turn depends upon daily
Fig. 1—Full scale HYDROPERM demonstration unit.
CYANIDE
CLARIFIER NEUTRALIZATION DESTRUCTION SUMP
TANK TANK
SLUDGE
r*
OVERFLOW
TAN
SEWER LINE
t
PERMEATE
t
CAUSTIC
K
— *-
T
ACID
WASTE-
WATER
WASTEWATER
PROM
^ ALKALINE
PLATING
BATH
' Fig. 2—Wastewater treatment flow diagram at Craftsman Plating and Tinning
Corp.
changes in the plating operations and subsequent changes in
treatment. As a result, the suspended solids loading to the
microfiltration system varied widely.
In several incidences, there seemed to be no flux decline
during the day. On other days, however, dramatic changes
were noted; likely the result of poor physical and chemical
control of the pretreatment steps. For example, during the
June 15th run (see Table 1) the plateau flux was less than
2040 l/m2/day (50 gal/ft2/day) and the total solids (TS) in
the permeate were abnormally high. The pH value that day
was around 6 to 7, which was too low to effectively
Table 2
Laboratory Analyses on Metals in the Battery Wastewater Effluents
Date
2-27-80
4-2-80
9-24-80
11-11-80
12-12-80
Samples
Feed
Permeate
Feed
Permeate
Feed
Permeate
Feed
Permeate
Feed
Permeate
TS
mg/l
162,740
3,621
12,364
3,378
9,346
2,773
1 1 .932
3,356
7,794
3,358
SS
mg/l
160,000
1.8
9,188
1.0
6,804
1.0
9,180
6
5,144
14
Pb
mg/l
0.045
319.4
0.029
40.3
0.082
55.2
0.073
84.4
0.064
Cu Zn Ni Sb As
mg/l mg/l mg/l mg/l mg/l
54.5
0.017 0008 0.24 0141 0.002
- — - 0.151 <0.002
0.023 0.024 0.053 0.058 0.003
0.015 0016 0.041 0190 0.001
57
-------
Fig. 3—Flux decline as a function of lime.
precipitate a heavy metal such as cadmium.
During the eight-week evaluation, the plateau fluxes
varied from the lowest value of less than 2040 l/m2/day (50
gal/ft2/day) to values over 16,300 l/m2/day (400
gal/ft2/day). The average flux varied between 6110 to 8150
l/m2/day (150-200 gal/ft2/day). This range was very similar
to the results derived from the preliminary laboratory
studies.
The permeate quality during the evaluation indicated, as
shown in Table 1, that the microfiltration system was
capable of removing suspended metals in the wastewater
stream. Typically, in the effluent of the microfiltration
system, cadmium was less than 0.5 ppm and suspended
solids were less than 10 ppm when pH control was properly
maintained.
Microfiltration System Application Study
The first full-scale HYDROPERM® microfiltration system
was installed at the General Battery Company, Hamburg,
Pennsylvania, in December, 1979. This system was a part of
the total wastewater treatment system to remove suspended
heavy metals from battery-manufacturing wastewaters.
The wastewater from lead-acid battery manufacturing is
typically highly acidic with an approximate pH of 1 and
contains a number of heavy metals including lead, antimony,
arsenic, cadmium, nickel and copper. Some of these metals
can appear in concentrations varying from 20 to 200 ppm.
The wastewater lead-acid battery manufacturing
characteristics can be considered to be similar to those of
electroplating wastewaters with the exception of the absence
of cyanides and hexavalent chrome. The conventional waste
treatment technology for both industries is similar.
Conventional neutralization/precipitation processes and
solid/liquid separation processes are widely used.
Two MF units were designed, constructed, and installed
at the General Battery plant with a combined wastewater
treatment capacity of 188,000 Ipd (50,000 gpd). Figure 3
gives a schematic of that system. Slaked lime was used in the
neutralization tanks. No other chemical additives or
flocculants were added. The systems have been operating
since February 1980, and are maintaining an average flu.
rate of over 16,300 l/m2/day (400 gal/ft2/day). Currently, th
permeate from the systems is of sufficient quality that it i
being discharged to a public waterway without further treal
ment. Table 2 shows the tested permeate quality analyse
from these systems.
CONCLUSION
Cross-flow microfiltration is an effective treatmen
technology to serve as unit process in the treatment train fo
industrial wastewaters containing heavy metals. Thi
precipitated heavy metals formed by either caustic addition
as in the electroplating study, or lime addition, as in thi
battery study, can be easily separated from the wastewater i
its pH is well controlled. Two full-scale microfiltration unit;
installed at the Hamburg plant of General Battery have beet
successfully operating for two years. The quality of th<
treated wastewater is sufficient to permit discharge to publi<
waterways or to local waterworks in the state o
Pennsylvania. Although the electroplating evaluatior
program was conducted for only eight weeks, the result;
were similar to the results of the battery wastewatei
program. The resulting effluent is being discharged to thf
local public waterworks. Both evaluations indicate thai
microfiltration is a technology that can filter toxic heavj
metal suspensions from industrial wastewaters.
ACKNOWLEDGMENT
The authors wish to acknowledge the financial support
from the U.S. Environmental Protection Agency, Industrial
Environmental Research Laboratory, grant No. S-805748-
01 for battery wastewater application, and the Office of
Exploratory Research, grant No. R-807503-01-0 for
electroplating wastewater application. Valuable assistance
from the following corporations and organizations was also
sincerely appreciated: General Battery Corporation,
Pennsylvania; American Electroplating Society; Alexandria
Metal Finishers, Virginia; Craftsman Plating and Tinning
Corporation, Illinois; and Chrome-Rite Corporation,
Illinois.
REFERENCES
1. Henry, J. D., Jr., "Cross-Flow Filtration", Recent
Development in Separation Science, Volume V, CRC
Press, 1972, pp. 205-225.
2. Tulin, M. P., "Cross-Flow Filtration", Paper presented at
Fine Particle Society Fall Meeting, September 16-18,
1980, University of Maryland.
3. Shapira, N. I., Liu, H. L. Baranski, J., and Kurzweg, D.,
"Removal of Heavy Metals and Suspended Solids From
Battery Wastewaters: Application of Hydroperm
Crossflow Microfiltration", U.S. Environmental
Protection Agency, EPA-600/S2-81-147, September,
1981.
This paper has been reviewed in accordance with the U. S,
Environmental Protection Agency's peer and administra-
tive review policies and approved for presentation anc
publication.
.58
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The Application of Ion-Exchange
and Modified Rinsing Procedures
to Minimize Treatment Costs
Donald W. Kemp, Ph.D.*
INTRODUCTION
The capital cost of treating wastewater generated from
a metal finishing operation is primarily a function of the
rinse water volume to be treated. Many wastewater treat-
ment systems installed during the 1970's were oversized since
water conservation measures were not always fully
exploited. It is anticipated that systems designed during the
1980's in response to the pretreatment regulations will be less
costly due to the increased awareness of this factor.
However, the approach of minimizing water usage does
not necessarily result in the lowest cost treatment system. It
would be more cost-effective to focus on minimizing the
quantity of process chemicals lost in the drag-out and to
segregate residual drag-out loads into small rinse volumes
that can be recovered or treated in a simple and inexpensive
batch treatment system. By reducing pollutant loads
discharged from the process line, operating costs as well as
capital costs can be minimized. Background information on
this approach is described below with an example of a
system design to illustrate the application of in-line process
controls.
DRAG-OUT CONTROL
The most effective pollution control measure is to keep the
process chemicals in the process bath. This is most frequently
accomplished by incorporating more effective drainage of
drag-out from the work with longer drain times or
modifying the position of the work. Methods to decrease the
quantity of process chemicals lost in drag-out include
reducing the chemical concentration in the process bath and
installing exit sprays.
The actual reduction in drag-out losses that can be
realized is strongly dependent on existing plant practices and
the ability of plant management to initiate corrective action.
It is not unreasonable to anticipate reductions in process
chemical losses in the 25-50% range along with
corresponding reductions in capital and operating costs.
Because of these potential opportunities it would be prudent
for plant management to initiate a process assessment to
identify feasible alternatives that would be practical to
implement. A more detailed description of point source
controls has been recently published by EPA1 which would
provide background for this assessment.
DRAG-OUT SEGREGATION
The next line of defense to keep the process chemicals out
of the rinse water is to segregate the drag-out in a still rinse or
a slow rinse. The rinse concentrate can be returned to the
*Donald W Kemp, Ph D
Raytheon Ocean Systems Co
East Providence, Rl
process as evaporative make-up or batch treated. This
approach requires the use of multiple rinse stations,
however, space constraints can be a limiting factor. Off-line
concentration of the drag-out can be accomplished by
evaporation, electrolytic deposition, ion-exchange, or with
membrane processes such as reverse osmosis and
electrodialysis. These processes are relatively expensive and
before they are seriously considered, a thorough evaluation
of in-line process controls should be completed. Frequently,
the addition of one or two rinse tanks in the process line
can achieve similar results at far lower capital and operating
costs.
The use of a drag-out recovery still rinse, followed by a fast
rinse, is widely employed to recover process chemicals in the
drag-out from a heated plating bath. It is less widely applied
to control the contamination levels in the fast rinse to
minimize the size and cost of a treatment system. A slow
rinse can be used to remove the major fraction of the process
chemical in a drag-out followed by a fast rinse to reduce the
residual drag-out load to acceptable contamination levels for
quality control purposes. If the residual load in the fast rinse
is sufficiently low, it can be discharged without treatment
since other non-contaminated rinses would provide a
dilution factor. Alternatively, the lightly contaminated fast
rinse can be economically treated by an ion-exchange
process.
Generally a minimum of three and preferably four rinse
tanks would be necessary to provide sufficient flexibility to
adjust flow rates to achieve an acceptable degree of rinsing in
the final or fast rinse and concentrate the pollutants in the
slow rinse. Examples of alternative rinsing modes that could
be considered under different process conditions are shown
in Figure I.
Fig. 1—Alternative Rinsing Modes.
59
-------
With a cold bath, the slow rinse concentrate can not be
returned to the bath as evaporative make-up and would be
discharged for batch treatment unless it was economical to
consider an off-line process such as an electrolytic recovery
unit. With a heated bath a closed loop rinsing system is
shown where a sufficient degree of rinsing is achieved in the
final rinse and all of the process chemicals are returned to the
plating bath. Insufficient evaporation occurs with a warm
bath to achieve high recovery by returning the slow rinse as
evaporative make-up. In the example shown in Figure 1, a
pre-dip in the rinse concentrate increases the recovery
efficiency since process chemicals rather than rinse water are
dragged into the plating bath.
To illustrate how drag-out losses can be reduced for a
heated bath alternative rinsing modes are shown in Figure 2
for a heated Watts nickel bath. These baths are generally
operated at 140-145° C with nickel salt concentrations in the
40-45 oz/gal range and typically have one drag-out recovery
tank followed by one or two fast rinses. As shown in the first
example, this would result in about one pound of nickel
discharged into the final rinse assuming a drag-out loss of 1
gph over one shift.
The quantity of nickel discharged for treatment can be
reduced by a factor of approximately 10 by decreasing the
salt concentration and increasing the bath temperature by
10°F which almost doubles the evaporation rate. By
operating the three rinse tanks as a 2-stage CF slow rinse
followed by a single stage fast rinse 97% of the nickel can be
recovered and 54 grams of nickel will be discharged
compared to 520 grams in the first example. However, the
nickel concentration in the final rinse is 14 mg/1 versus 1.1
mg/1 at the 2 gpm flow rate.
Another rinse tank can be added as shown in the third
example to reduce the concentration. The evaporation rate
could be doubled by increasing the bath heating time or by
adding air agitation. The resulting 80 gpd flow in the 2-stage
CF slow rinse would result in 99.8% nickel recovery and a
residual nickel level of approximately 4 mg/1 in a single stage
2 gpm rinse.
END-OF-PIPE TREATMENT
The driving force to control drag-out losses is to avoid the
high cost of treating large volumes of lightly contaminated
rinse water in a large treatment system that consumes
valuable floor space in a non-productive activity. The capital
cost for a conventional treatment system involving metal
hydroxide precipitation is shown as a function of flow raU
Figure 3. These costs range from about $4000/gpm at I
low flow rate, decreasing to about $2000/gpm at the hi
flow rate. Lower costs are associated with the batch reacti
tanks that are made of plastic instead of coated steel.
Ion-exchange represents an end-of-pipe alternative tc
conventional treatment process that can achieve a higl
quality effluent. However, it has not been widely employ
in the metal finishing industry because of higher overall co
that are associated with regenerating the spent resin.
A comparison of the capital costs curves shows that t
ion-exchange treatment system is approximately one thi
the cost of a conventional treatment system. A relativt
smaller cost would need to be added for a small ba
treatment system to process ion-exchange regenerate, spe
process solutions, floor spills, and other miscellaneous k
volume, concentrated process discharges.
The higher operating costs for ion-exchange can be off!
by taking a credit for the lower water usage by recycling t
deionized water produced during treatment. With this crec
ion-exchange can be less costly than a metal precipitati
process particularly in those cases where the cost of wa
includes a sewer use fee. A detailed cost evaluation and an:
depth description of the application of ion-exchange in t
metal finishing industry has recently been published
EPA.2
ION-EXCHANGE POLISHING
The operating cost of ion-exchange can be significant
reduced if the system is operated as a polishing process rath
than a primary treatment process. This can be accomplish
by modifying the rinsing procedures in the process line
include the following:
1. Slow rinse - utilize a slow rinse to remove the
majority of the ionic contaminant load in the drag-
out; recover the rinse concentrate or treat the small
volume in an inexpensive batch treatment system.
2. Fast Rinse - utilize a fast rinse to reduce the residual
contaminant load in the drag-out to acceptable
levels; process the lightly contaminated rinse water
in an ion-exchange unit with periodic batch treat-
ment of the regenerate.
This approach allows the major fraction of the hydrau
load to be treated with a lower capital cost compared to th
by conventional treatment.
The operating cost is directly related to the regeneratii
Fig. 2—Nickel Rinsing Alternatives.
I COST COMPARISON
ION-EXCHANGE
50 75 LOO 125 150
WASTEUAT6R FLOW (CPK)
Fig. 3—Capital Cost Comparison.
60
-------
frequency which in turn is a function of the flow rate set in
the slow rinse. As shown by the curves in Figure 4 for a single
and 2-stage CF chrome rinse, the regeneration frequency can
be readily reduced by a factor of 10 or greater, along with
corresponding reductions in operating costs.
In this example, one cubic foot of resin would saturate in
approximately 2.5 hours if a 1 gph drag-out from a 40 oz/gal
chrome plating bath were processed through the resin.
(Resin capacity: 30 equivalents/ft3). With a slow rinse set at
70 gpd, for example, the regeneration frequency would
increase by a factor of 10 for a single stage rinse and a factor
of 90 with a 2-stage CF slow rinse.
One objective in setting a slow rinse rate is to minimize the
regeneration frequency and therefore the operational costs.
A second objective is to minimize the volume of wastewater
to be treated to minimize the capital costs. This volume
consists of the slow volume and the ion-exchange regenerate.
The latter includes the acid and caustic used to regenerate
both the cation and anion columns and the slow and fast
rinses. Typically about 10 column-volumes or about 150
gallons/ft3 of contaminated wastewater are generated during
cation and anion regeneration and require treatment. This
volume can be reduced because not all of the fast rinse
volume requires treatment. This, however, is offset
somewhat by the need to periodically treat backwash water
from the filter that precedes the ion-exchange column.
The average daily volume of regenerate per cubic foot of
resin that would require treatment is shown as a function of
the regeneration frequency in Figure 3. The point of
intersection with the slow rinse curves represents the point
where the total volume requiring treatment is minimized.
For example, with a drag-out of 1 gph, a volume of 100 gpd
or 50 gpd would require treatment depending on whether a
single or 2-stage CF slow rinse is employed.
The data in Figure 3 illustrate that the operating cost of an
ion-exchange process can be significantly reduced by using a
slow rinse to reduce the ionic load discharged to the ion-
exchange system. By coupling point source controls to
minimize drag-out losses with ion-exchange treatment to
Ale.
Rl
M
E.G.
Rl
R2
1
Cu
Srk.
Rl
R2
R3
kcidl
Fig. 4—Ion-exchange Regeneration Frequency as a Function of Slow Rinse
Flow Rate.
i r
HI
C- ,li
111
1 1
t
-\f
0
t-
1
c,
Dip
1|
-v x~vt>-
0.3 |pd t
Chzn
•*.
.1.
M
Nickel
0.05 Bpa D.I 2 gp» D.I 2
+ A d
rrajt]
ILJPLLJ
Rl | R2 IJAcld Cla.n
t '
SJJd Tip 2
Alkaline 5o»k
1 V-
Hl
IP"
^
Rl
--I
R2
T«P £
2
1
Bitch + Batch
Sewer (IX)
Fig. 5—Automated Line.
Rl
R2 Nickel Rl
R2
R3
P04
Rl
\ fj i '
Acid
I
Rl
R2
Sewer
CN Batch
Sewer
Sewer
Hvy.
Au
n
Rl
I
Evap
R2
R3 1 1 Lt . Au
L
Rl
|
Evap
R2
R3
Set
IRI
R2
1
1 Ag j
j£y
Electr
Reco
Ag
Reco
Rl
R2 Rl
R2
Rh
I"'
R2
R3
Olylic . T T T 1
very L ' | |
CN Batch Sewer
Fig. 6—Precious Metal Line.
61
-------
6.3
Automatic
Line
o
w
vO
,
i
IJ
6 . f* pp"1^
Precious
Line
•Acidic
Alkaline Q
oor Drain "<
Chrome ^
Uncontatninated ,
Ion Exchange
6
&
u-i
1
b
c
0
r~
q
3. 1 Pryg
II f Acidic
* Alkaline
Floor Drain o.
O-anide
Unccntaininated
Ion Exchange
OB
i — i
Hand
Line
i
i
e
a.
60
in
ol
It.
I 'I 1 Acidic
1 — i Alkaline
"Floor Drain
Cyanide
Chrome
Uncontaminated
Ion Exchange
1 gpm
No
Scheduled
0.2 gpm Batch Dumps
Cyanide
Sump
Alkaline
Sump
i
0 . 6 gpm
1
Floor
Drain
Sump
!
B.
3tch Dumps Discharge
1 i
Acid
Sump
Chrome
Sump
9 gpm 4 . 5 gpm
J 1
Ion
Exchange
lAniqn J
Regenerate |
Cation
Jn contam-
inated
Sump
Disposal
d
Sludge
Dewatering
Tank
. 5 gpm
2.5
Sludge Wactor Treated
---. E£fluent.
16 gpm Sewe
Fig. 7—Wastewater Flow Schematic.
remove residual process chemicals in the rinse water, a cost-
effective treatment system can be designed.
DESIGN OF A POINT SOURCE CONTROL SYSTEM
An example of how point source controls can be applied
to minimize treatment costs has been demonstrated in one
facility design for a plant that manufactures mechanical pens
and pencils. The existing metal finishing operation
incorporated an automated chrome line and a low volume
hand line that included copper, brass, nickel, and chrome
plating. The operation was to be moved to a new location
and expanded to include a manual precious metal line. The
company required a wastewater treatment system to be
designed to satisfy the sewer use ordinance which included
the following limits (mg/1): CN - 0.5; Cu - 1.0; Ni - 3.0; Cr -
3.0; Ag - 0.03).
A systematic evaluation of each process bath was
conducted to define process specifications that would
minimize treatment costs and process chemical losses. The
approach focused on reducing drag-out losses and the use of
counterflow rinsing to minimize the volume of wastewater
requiring treatment.
Automated Line
The automated chrome line involves rack plating of a
variety of brass components that include tubular pieces.
Drag-out rates in the existing line were measured to be 1 -1.5
gph. It was determined that the majority of the drag-out
could be more effectively drained by tilting the rack and a
redesigned rack will be used for rack replacements.
The layout of the new automated line is shown in Figure 4
and consists of a single stage rinse after the alkaline soak ani
a 2-stage CF rinse after the acid cleaning bath with th
discharge used as the supply for the 2-stage CF rinse after th
electroclean bath. The soluble copper concentration in th
cleaning bath was found to approach 150 mg/1 near the em
of the 2-3 week cleaning cycle. It was calculated that thi
would result in a copper concentration in the combinei
discharge in excess of the 1 mg/1 limit toward the end of th
cleaning cycle. To offset this factor, exit sprays were specifiei
in each of the three cleaning baths which would enable th
rinse water to be discharged to the sewer without treatment
As a precaution the discharge could be directed to an ion
exchange unit which was sized to process the rinse wate
from all the cleaning baths in the automated and manua
lines.
Four CF rinses were used after the 1800 gallon nickel ball
(heated at 150°F) to close the rinsing loop and recover 1009
of the nickel salts. The standby capacity in the off-lim
evaporation tank and facilities for air agitation in the nicke
tank would enable the slow rinse to be increased if required
All of the slow rinse concentrate is returned to the bath a;
evaporative make-up via the exit spray by pumping fron
R4. A conductivity flow control in Rl would enabli
additional water to be added if necessary and any exces:
rinse water that could not be returned as evaporative make
up would be pumped to the evaporation tank or dischargee
to batch treatment.
The chrome rinsing sequence consists of a 3-stage CF slov
rinse (0.05 gpm) with recirculation from R3 to a chrome pre
dip tank. A stand-by tank provides additional holdinj
62
-------
capacity to evaporate any excess slow rinse that can not be
returned to the chrome bath via an exit spray pumped from
R3. Over 95% recovery is expected. The 2-stage CF final
rinse would remove the residual chrome in the drag-out to
achieve a final calculated chrome concentration of 1 mg/1.
The final rinse would be discharged to an ion-exchange unit
to remove the residual chrome which is estimated to be less
than 250 gms/day.
Precious Metal Line
The precious metal line involves manual rack plating of
gold, silver, and rhodium. The rinsing system in this line was
directed at achieving the following objectives:
1. close loop rinsing after the nickel bath
2. recovery of greater than 99% of the gold and
rhodium
3. segregation of greater than 90% of the cyanide load
from the copper strike and silver baths into a slow
rinse
4. reduction of water usage by inter-loop rinsing
where feasible.
A drag-out rate of 0.5 gph was assumed in the calculations to
determine concentrations, flow rates, and optimum
arrangement of rinsing tanks.
In the cleaning line it was established that a 3-stage CF
rinse after the copper strike and nickel baths would be
adequate to satifsy the rinsing objectives. A conductivity
flow control would be used to ensure that acceptable
concentration levels would be maintained in R3. With a slow
rinse flow rate set 25 gpd to match the evaporation rate in the
nickel bath essentiallly 100% of the nickel salts would be
recovered. Back-up evaporation capacity in the 150° F nickel
bath is available through air agitation if an increase in the
slow rinse flow is required.
In the gold line an off-line air agitated evaporation tank
was used to further concentrate the slow rinse from the 3-
stage CF rinse after the heavy and light gold baths. By
returning the concentrate to the heated gold baths
(110-120° F) as evaporative make-up, 99% of the gold could
be recovered. This approach eliminated the need to use an
off-line gold recovery process. If it is established that gold
leakage from inefficient rinsing occurs, it would accumulate
in the set rinse and an ion-exchange unit would be installed
to recover the residual gold.
The rinsing sequence after silver plating consists of an
electrolytic recovery rinse followed by a 2-stage CF slow and
fast rinse. The slow rinse flow of approximately 25 gpd was
calculated to segregate over 99% of the cyanide load. The
residual cyanide load in the fast rinse would result in an
acceptable effluent concentration after dilution with the
other rinse water.
A 3-stage CF closed loop rinse was employed after the
rhodium bath to recover over 99% of the rhodium by
returning the slow rinse to the bath as evaporative make-up.
The evaporation rate is maximized by employing air
agitation in the bath at elevated temperatures during periods
of non-plating activity.
WASTEWATER TREATMENT SYSTEM
As shown in the wastewater flow scheme in Figure 7, 16
gpm of wastewater is expected to be generated from the three
process areas. The only sources that require treatment are:
• 2 gpm of lightly contaminated chrome rinse water
• approximately 100 gpd of cyanide contaminated
rinse water
The remaining wastewater can be discharged to the sewer
without treatment as the residual contamination levels
would be below the EPA limits promulgated in the
Electroplating Pretreatment Regulations and the more
stringent local sewer use limits.
The 100 gpd of cyanide contaminated rinse water would
be discharged to a 600 gallon reaction sump and batch
treated on a weekly basis. The contaminated chrome rinse
water would be processed in an ion-exchange unit which has
an anion resin capacity (4 ft3). This would enable the unit to
be operated for over four weeks before regeneration would
be required. The regenerate would be batch treated in a 500
gallon reaction sump to reduce the hexavalent chrome to
chrome III.
The ion-exchange system which costs approximately
$16,000 is a skid mounted semi-automatic unit that consists
of a sand filter, a carbon column, and a cation and anion
column each containing 4 ft3 of resin. The system which has
a hydraulic capacity of 8-12 gpm was sized to process rinses
from the cleaning, chrome, and silver baths. Initially the
deionized water (DI) produced in the system will be
discharged to the sewer and the installation of a DI water
recirculation system will be delayed until after the metal
finishing operation is brought on-line in the new facility.
Plant management elected to install a second back-up ion-
exchange system which will be used initially to provide DI
water for the metal finishing operation using town water
rather than wastewater as the supply source.
The remaining wastewater sources include:
• schedule batch dumps
(normalized over cleaning cycle): 300 gpd
• vibrator discharge (design specification): 500 gpd
• floor spills (estimated): 300 gpd
Total 1100 gpd
These discharges would be directed to the acid, alkaline,
and floor drain sumps and pumped to a 3000 gallon batch
reaction tank to neutralize the combined discharge and
remove metallic fines and soluble metal.
SUMMARY & CONCLUSIONS
The facility design described above illustrates that in-
process controls can be integrated into a process line to
maximize recovery of process chemicals and significantly
reduce treatment costs. The success of this approach is highly
dependent on plant management initiating a detailed process
evaluation to identify procedures to minimize drag-out
losses and to locate sufficient space in the process line to
incorporate additional rinsing. This approach would enable
ion-exchange to be considered as an economical alternative
to conventional treatment involving metal hydroxide
precipitation.
REFERENCES
1. Control and Treatment Technology for the Metal
Finishing Industry, In-Plant Changes. EPA Summary
Report, January, 1982. Industrial Environmental
Research Laboratory. EPA 625/S8-82-008.
2. Control and Treatment Technology for the Metal
Finishing Industry, Ion Exchange. EPA Summary
Report, June, 1981. Industrial Environmental Research
Laboratory. EPA 625/S8-81-007.
The work described in this paper was not funded by the
U.S. Environmental Protection Agency and therefore the
contents do not necessarily reflect the views of the Agency
and no official endorsement should be inferred.
63
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Recovery of Acid Etchants at Imperial Clevite Inc.
William J. Herdrich*
ABSTRACT
Imperial Clevite recovers two etching solutions at its plant in Niles, IL, a chromic acid-
sulfuric acid etching solution and a nitric acid solution. The chromic acid-sulfuric acid
etching solution is regenerated and recycled through a unit developed by the U.S. Bureau
of Mines. The nitric acid solution is recycled through a unit made by Eco-Tec Ltd. of
Canada.
The Bureau of Mines unit has regenerated and recycled etching solution from a
chromating operation for brass parts during normal production for six months. The
etching solution has been maintained at an acceptable level of performance, and
consumption of sodium dichromate has been reduced by 70%. Waste generation has been
reduced by 76%, and the cost of the operation has been reduced 73%.
The Eco-Tec unit has only been in operation for a few days as of this date. Results, so
far, look positive.
INTRODUCTION
Imperial Clevite Inc. is a multi-divisional company whose
operating divisions are based upon similarity of products.
The Fluid Components Division is one such division. The
Fluid Components Division produces products relating to'
connection and control in fluid power systems. The,
division's valves, fittings, testing devices and tubing tools are
used in process instrumentation control, truck air brake
components, refrigeration evacuation, pneumatic and other
air devices.
In the production of these products the Fluid
Components Division operates a plating and metal finishing
operation. This operation produces wastes which must be
controlled. In 1980 while designing and installing a system to
control these wastes, means of recovering and recycling
chemicals and metals were investigated. As a result of these
investigations it was determined that the "bright dipping"
operation, a chemical surface treatment used to give brass
parts an attractive appearance and provide corrosion
resistance, produced the most chemical and metal waste and
that it might be possible to recover some of this waste.
"BRIGHT DIPPING" OPERATION
The "Bright Dipping" Operation is used to give brass parts
an attractive appearance and provide corrosion resistance.
This is very important for forged brass parts to remove the
scale and oxides present after forging. The process consists
of muriatic acid etching to remove scale and oxides, nitric
acid etching to provide a very smooth, bright finish, and a
chromic acid-sulfuric acid etching to provide a lustrous
finish while applying a corrosion resistant coating. A
noticeably less attractive finish indicates failure of one or
more of the etching solutions. Failure of the etchants results
from an increase in the concentration of dissolved metals or
*William J, Herdrich
Imperial Clevite, Inc.
Chicago, IL
a decrease in the free-acid content of the solution. The
chromic acid-sulfuric acid etchant is also quite sensitive tc
increases in chloride contamination, which is caused b}
drag-in of the muriatic acid etchant. Failure of the chromic
acid-sulfuric acid etchant is very noticeable as a dull, mottled
finish on the part with a slightly red coloration, which gives
an extremely unattractive appearance. Usually failure of the
etchant solutions can be delayed by simple additions, but the
working life of the solutions cannot be significant!}
lengthened. When the etchant solutions degrade beyond the
point of rejuvenation by chemical addition, they are
chemically treated by standard methods to produce a low-
grade sludge containing 1 to 10 percent solids.
Of the three etchants used in the bright dipping operation
only two, the chromic acid-sulfuric acid etchant and the
nitric acid etchant were chosen for recovery based on cost.
Recycling of Chromic Acid-Sulfuric Acid Etchant
The recycling of chromium is not new. The Bureau of
Mines has been engaged in research on the subject for some
time, and it happened that in 1980 they had developed a test
unit for the recycling of chromic acid-sulfuric acid solutions
and were looking for a test site. Imperial Clevite's Fluid
Components Division, then the Fluid Components Division
of Gould Inc., volunteered to be the test site since the Bureau
of Mines test unit had a direct application to its operation.
The unit designed by the Bureau of Mines was an
electrolytic acid recovery system. The technology for the unit
was described at this conference last year by representatives
of the Bureau of Mines.1 Basically, the unit oxidizes trivalent
chromium to hexavalent chromium and simultaneously
recovers copper and zinc. The unit uses anode membrane
cells in a catholyte tank. The copper is recovered as a solid
and the zinc remains in the catholyte solution.
The test was conducted from May 31 to June 16, 1980.
Calculated results from the test showed that 40.9 percent of
the Cu contamination was removed, 21.1 percent of the Zn
contamination was removed, and 81.2 percent of the
trivalent Cr was converted to hexavalent Cr. Table I shows
64
-------
Chemical Analysis of
Etching Solution
Bureau of
Spent CSA etchant
CSA etchant during
operation (average)
CSA etchant at end
of operation
Table 1
Chromic Acid-Sulfuric Acid (CSA)
Before, During, and After the
Mines Unit Operation2
Cr" Cu
(pet) (g/l)
86 5 8.0
94.0 3.2
99.3 1.3
z« a
(g/0 (ppm)
3.7 320
2.0 64
2.0 5
analysis of the etchant samples during the test.2
The optimum conditions for chromic acid-sulfuric acid
etchant are: pH of 0.8 to 1.2 and 8 oz/gal Na2Cr2O7-2H2O.*
Prior to the use of the Bureau of Mines test unit preparation
of the etchant required 50 Ibs of Na2Cr2O7-2H2O. Periodic
additions were made to maintain optimum operating
conditions. After approximately two days and
approximately 36 Ibs of additions, the etchant became
ineffective and was treated and discarded. Therefore, the
average weekly consumption of Na2Cr2C»7-2H2O was 215
Ibs. Treatment and disposal of the etchant generated
approximately 1,750 gal/wk of low grade sludge.
During the Bureau of Mines test the weekly
Na2Cr2O7-2H2O consumption was 56 Ibs. The waste
produced by the unit created approximately 125 gal of
sludge per week. This was a drastic reduction from the 215
Ibs/wk of Na2Cr2O7-2H2O and 1,750 gal/wk of sludge
produced during normal operation.
Based on the results of the Bureau of Mines tests, Imperial
Clevite contracted for Scientific Control Laboratories to
produce an industrial model of the Bureau of Mines test unit.
This unit was completed in January of 1981 and in operation
by March of 1981. Except for some minor problems causing
shutdowns for short periods of time, the unit has been
running consistently since March 1981. Since installation of
the unit, consumption of Na2Cr2C>7-2H2O has been
approximately 50 Ibs/wk. Sludge produced has been
approximately 200 gal/wk.
The major costs of operating the chromic acid-sulfuric
acid etching solution are Na2Cr2O?-2H2O consumption and
sludge haulage. The market price for Na2Cr2Or2H2O is
approximately $.68/lb. Prior to installation of the recovery
unit the operation consumed 215 Ibs/wk costing $145/wk.
Sludge haulage charges for the Niles area are approximately
$.20/gal. Cost of hauling the 1,750 gal/wk produced prior to
installation of the unit was $350. The total of these major
costs for operating a chromic acid-sulfuric acid solution
prior to installation of the recovery unit is $495/wk. Since
installation of the Scientific Control Unit, Na2Cr2C*7-2H2O
consumption has been averaging 50 Ibs/wk at a cost of
$34/wk. The unit produces approximately 200 gal/wk of
waste to be hauled costing $40/wk. Based on these figures
the cost of operating the chromic acid-sulfuric acid solution
with the recovery unit is approximately $74/wk. Also the
copper is recovered in a solid form. In the first four months
of operation, 500 Ibs of 98% pure copper were extracted
from the unit.
*Na:Cr:O7-2H:O is the chemical representation for sodium dichromate
The recycling unit for chromic acid-sulfuric acid solution
has been effective at maintaining the etchant at an acceptable
performance level and reducing the consumption of
Na2Cr2O2H2O. The reduction of Na2Cr2O7-2H2O and
sludge generation resulted in significant cost reductions. The
cost of Na2Cr2O2H2O usage and sludge haulage prior to
installation amounted to $495/wk. After installation, the
cumulative costs of Na2Cr2C>7-2H2O consumption and
sludge haulage amounted to $74/wk, resulting in a $421 per
week reduction in normal operational costs for these items.
Recycling of Nitric Acid Etching Solution
The recycling of nitric acid is done by an Acid Purifica-
tion Unit marketed by Eco-Tec Limited, Toronto, Canada.
The unit is designed to continuously maintain bath integrity
by removing metallic contaminations as they are generated.
As a result:
1. Acid purchases are reduced
2. Waste treatment costs are reduced
3. Process operation is stabilized
The Acid Purification Unit uses an ion-exchange resin bed
and recirculating flow to recycle the nitric acid. The resin
bed absorbs mineral acids leaving a de-acidified metallic salt
byproduct which is treated and disposed of. The acid is
removed from the resin bed by forcing water through the
resin with air pressure. The result is a purified acid which is
returned to the etching tank.3
Operation of the nitric acid etching solution without tne
Acid Purification Unit consumed approximately 400 gal/wk
of nitric acid and produced 3,500 gal/wk of waste. The
market price for nitric acid is approximately S1.43/gal. Fora
consumption of 400 gal/wk the direct cost is $572/wk.
Sludge hauling charges for the Niles area are approximately
$.20/gal. Cost of hauling 3,500 gal/wk is $700/wk. The total
cost then for operating the nitric acid etching solution is
$l,272/wk. Since installation of the Acid Recovery Unit,
nitric acid consumption has been approximately 200 gal/wk.
With the unit operating, the operation still produces 3,000
gal/wk of waste, eliminating only 500 gal/wk. Based on
these figures the cost of operating the nitric acid bath with
the Acid Recovery Unit is $868/wk, a savings of $386/wk.
CONCLUSION
The recycling of the acid etchants at Imperial Clevite has
been successful. The consumption of both nitric acid and
Na2Cr2C«7-2H2O have been reduced significantly. The cost of
waste hauling has been reduced, and the etching operations
run more consistently.
To a manufacturing organization the most important
aspect is the cost reduction. The cost savings for these two
operations will be approximately $40,000/yr.
REFERENCES
1. L. C. George, D. M. Soboroff, and A. A. Cochrou.
Regeneration of Waste Chromic Acid Etching Solutions
in an Industrial-Scale Research Unit. Third Conference
on Advanced Pollution Control for the Metal Finishing
Industry, EPA-600/2-81-028, February 1981 pp. 33-36.
2. Glenn L. Horter and Lawrence C. George.
Demonstration of Technology to Recycle Chromic Acid
Etchants at Gould, Inc. 1981.
3. Eco-Tec Limited. Acid Purification Unit Literature.
The work described in this paper was not funded by the
U.S. Environmental Protection Agency and therefore the
contents do not necessarily reflect the views of the Agency
and no official endorsement should be inferred.
65
-------
Recovery and Electrochemical Technology
Philip Horelick*
INTRODUCTION
I shall discuss the experience of a job shop with the
installation of an High Surface Area (HSA) electrochemical
Reactor and associated in-plant changes. The Reactor
has been installed to recover cadmium and destroy
cyanide on two plating lines.
My paper focuses on the practical aspects of the
technology, such as operating performance and cost
savings, and discusses process water and pollutant
reduction techniques that were instituted before the HSA
Reactor was installed.
ALLIED METAL FINISHING—BACKGROUND
Allied Metal Finishing, Inc., is a metal finishingjob shop
that has operated in Baltimore, Maryland, since 1947.
Our 35,000-square-foot plant employs 50 people working
three shifts a day. Sales are more than $1.5 million a year.
Our plant is a multipurpose shop with the following
major facilities:
• Automated powder coating line
• Fluid-bed tank
• Barrel line
• Anodizing line
• Hoist line
• Automated zinc line
• Hard chrome line
• Electroless nickel line
• Precious metals line
• Chemical mixing
Zinc and nickel plating account for the major part of
our company's total volume. Cadmium plating currently
accounts for 10 percent of the total volume and is
expected to increase.
Before the installation of the electrochemical
technology a«d the implementation of waste reduction
techniques, our effluent discharge was approximately
100,000 gal/d. The City of Baltimore, Department of
Public Works, initiated a monitoring program in 1975
to measure the pollutant concentration of electroplaters
and other industrial contributors to the city waste
treatment system. The monitoring indicated that the
Allied effluent would require some treatment in order to
meet upcoming Federal standards.
Although the deadline for electroplating wastewater
pretreatment was some time away, we decided to initiate
compliance efforts in 1979. The additional time would
allow for an analysis of various treatment alternatives
and would eliminate a last-minute rush to purchase and
'Philip Horelick
Vice President
Allied Metal Finishing, Inc.
Baltimore, Maryland
install equipment.
We approached the Baltimore Department of Public
Works to determine what parameters were of most
concern. The Department responded that cadmium was
its biggest problem, because high levels of the toxic
element in the sewage treatment sludge can reduce the
City's disposal alternatives.
The City's records (Table 1) indicated that Allied had a
maximum cadmium discharge of 1.50 mg/L. The 4-day
average ranged between 0.45 mg/L and 0.82 mg/L. The
1984 Federal pretreatment standards for cadmium allow a
maximum of 1.2 mg/ L for any one day and 0.7 mg/ L for 4
consecutive monitoring days. Therefore, we were on the
borderline of compliance.
We expected, however, to increase cadmium production
significantly in the future, which would invariably push the
cadmium concentration well beyond the Federal limit. We
had projected the increase in cadmium plating because many
platers around the United States have reduced or
eliminated their volume of cadmium plating owing to local
attitudes similar to that of the City of Baltimore. Thus there
is incentive to find a cadmium control technology because,
with fewer cadmium platers i;i existence, such a technology
may be a beneficial tool for future business. Therefore, our
efforts were initially focused on cadmium.
POLLUTION CONTROL PROJECT
Conferences and exhibits of the American Electroplaters'
Society (AES) and the National Association of Metal
Finishers (NAMF) provided a mechanism to view the
various pollution control devices available to the plating
industry. At a 1979 NAMF show in Chicago, we were
introduced to the HSA Reactor, an electrochemical
technology designed for the recovery of various metals,
including cadmium.
We were attracted to the HSA technology for two major
reasons. First, the electrochemical technology removes
cadmium without the use of treatment chemicals and
without creating a sludge, thus avoiding sludge
transportation and disposal costs, which most pollution
control experts agree are the major operating expenses for
pollution control systems. Second, in the approach
developed by HSA personnel, the HSA technology is used
as part of a general compliance strategy that includes
making manufacturing process changes to reduce water use
and pollutant loadings. End-of-pipe treatment is only
applied after less costly in-plant changes and point source
recovery techniques, such as the HSA Reactor, are
implemented.
After meeting with personnel from HSA and discussing
the advantages of the approach, we decided to use the HSA
compliance strategy and Reactor.
66
-------
Table 1
Allied Effluent Analysis
Concentration (mg/L)
Date
2/3/75
8/26/75
9/ 1 8/75
6/ I 0/76
3/ 17/78
5/26/78
6/8/78
11/9/78
6/22/79
3/18/80
11/17/80
3/23/81
6/17/81
10/6/81
12/1/81
Cd Al
1.50 5.0
1.11 3.8
— —
0.40 3.0
0.27 —
0.16 —
0.44 —
— —
— —
0.92 8.9
— —
0.43 1.14
— —
0.28 —
0.22 —
Cu
1.05
1.26
—
1.15
0.52
1.05
0.39
—
—
0.36
—
1.28
—
0.90
—
Zn
170
6.8
—
3.5
4.8
—
8.20
—
—
3.9
—
12.38
—
11.0
15.5
Ni Fe
2.3 ' 37.0
095 —
— —
0.05 14.0
4.85 — '
105.0 —
0.48 —
— —
— —
0.90 —
— —
2.46 —
— —
3.26 —
3.05 —
Cr(T) CN Pb
—
— — —
2.49 2.32 —
7.5 0.23 —
7.33 1.48 0.19
2.91 — —
2.82 — —
— — —
— — —
— — —
_ _ _
— —
__
5.0 11.6 0.46
4.29 7.54 —
pH
6.82
8.65
7.8
5.46
8.05
6.50
9.41
9.10
8.07
2.82
2.28
6.04
7.77
—
Daily
Flow'
(l.OOOgal)
116
116
116
155
98
98
98
98
127
66
66
t
+
t
t
1 Average daily flow for year indicated
tData for
1981 not yet available
Note. — Dash indicates not reported by the city.
SOURCE
City of Baltimore, Department of Public
Works, Bureau
of Water and Waste Water
PLANT ASSESSMENT
The compliance strategy was initiated with a plant
assessment survey, which involved a thorough analysis of
the plating operations that relate to pollutant sources and
water use. The procedures used by the survey team
included:
• Reviewing plant layout, including equipment
placement piping, and sewer line layout
• Reviewing plant operating practices and procedures
• Conducting a process water survey
• Sampling to determine the type, quantity, and nature of
pollutants
• Isolating and identifying the sources of pollutants
• Examining process water use
The findings of the survey were presented in a 75-page
report that provided a detailed breakdown of water use in
the shop, a chemical balance, and, most important, 46
specific recommendations for saving water and chemicals
and reducing pollution.
Some of the recommendations related to operating
practice such as instructing operators to turn off the main
water valve during breaks and other line stoppages. Others
involved the application of inexpensive devices to reduce
water flow automatically. For example, one effective
recommendation for Allied was to install timer devices on
two of the plating lines for the control of water flow. This
action was deemed appropriate because the amount of time
between loadings through the rinse tanks was significantly
long that with a constant flow most of the rinse water used
was wasted. The timer reduced water use on these lines by
over 65 percent.
Most of HSA's 46 recommendations have been instituted.
Others are planned or will be considered when individual
plating lines are overhauled. The results thus far are very
positive. Overall, we were able to reduce the rate of water
use by 52 percent. Savings in water and sewer costs alone
are about $7,000 per year as indicated in Table 2, which
presents a history of water use at Allied from 1974 through
1980. The HSA recommendations were instituted in
January 1980. That year our water use rate dropped from
127,000 gal/ d to 66,000 gal/ d. It is even more significant that
sales remained about the same during that time period. A
comparison of flow rate and sales are presented in Figure 1.
Chemical use has also dropped since the HSA
recommendations were instituted.This decrease is a result
of using drag-out tanks to capture plating solution and
return it to the baths.
HSA REACTOR
After implementation of the in-plant changes for flow and
pollution reduction, the HSA Reactor was installed.
The Reactor is an electrochemical technology and,
therefore, its operating principles are easily understood by
the average plater. The unit makes use of a carbon fiber
cathode, which has an enormous surface area to volume
ratio—approximately 1,000 times greater than that of other
types of reactors. This high surface area provides a greatly
improved mass transfer rate. The result is that the time
required to reduce the concentration of a metal in solution is
a small fraction of that, for instance, for catalytic or
fluidized bed reactors.
Table 2
History of Water
Use:
1974 to Present
Year
1 974
1 975
1976
1 977
1 978
1979
1980
Consumption
galjd gal/min
228,000 158
116,227 121
155,724 108
125,998 87
97,888 68
127,186 88
65,777 46
$jl,000
gal
0.34
0.37
0.40
0.46
0.52
0.52
0.58
Cost
$1 Year
20,504
11,130
16,574
14,944
13,356
17,227
9,928
67
-------
1971 J9751976 197719781979 19BO
Year
1971 1975 197S 1977 1978 1979 1980
Year
Fig. 1—Comparison of Water Use and Sales: 1974-1980.
In addition to recovering metal and returning it to the
plating bath for reuse, the Reactor can electro-oxidize and
destroy cyanides below detection limits at a cost much
lower than the conventional alkali-chlorination process.
The Reactor originally installed at Allied was a
prototype unit. After HSA had fully developed the
technology, the current commercial unit replaced the
prototype.
Initially the Reactor was used to recover cadmium from
the barrel line only. Recent piping changes have been made,
however, and the Reactor now services the hoist line as well.
The Reactor itself is a skid-mounted unit needing
approximately 20 square feet of floor space. The space
requirement includes the microprocessor control, which
regulates solution flow during the process cycle and
automatically reverses the system to a strip cycle for metal
recovery.
Figure 2 shows the HSA Recovery System in a single line
arrangement. The solution from the process rinse is
pumped through a filter to remove particulate matter, and
through the Reactor modules, which house the high-
surface-area carbon fiber cathode. The treated water is
returned to the process tank. The power for the treatment
process is supplied by a common rectifier.
When the hoist line was added to the system (Figure 3),
the flow from the Reactor went first to the hoist line process
tank, then was pumped to the barrel line process tank and
back to the Reactor for cadmium removal and cyanide
destruction.
Although the HSA Reactor is capable of recovering in
excess of 99.9 percent metal pollutants, it is not necessary to
achieve such high levels at our plant in order to meet
existing environmental regulations. Current needs call for a
system equipped with only two modules; however, the unit
is capable of housing up to four modules, thus providing an
easy means to meet future higher capacity requirements.
The operation of the Reactor system is fairly simple and
not time consuming. Our unit is operated by the company
chemist, Julius Schattall. When the cadmium plating line is
used, Julius starts the Reactor by pushing a button, which
initiates the process cycle, and the solution from the process
rinse is pumped through the modules for cadmium removal
and cyanide oxidation. When plating is completed, pushing
a second button stops the process cycle and initiates the
strip cycle. When stripping is completed, the unit shuts
down automatically.
The strip solution is made up using sodium cyanide. The
concentration of cyanide in the solution is monitored
periodically and is kept in a range of 50 to 100 g/L. The
volume of the strip tank is about 135 gallons.
The strip solution remains in the strip tank for several
operating cycles, gradually increasing in cadmium
concentration. The maximum allowable concentration is 60
g/L. When the solution level in the plating bath is
sufficiently low, a part or all of the strip solution is pumped
to the bath to complete the recovery process. The strip
solution is not pumped to the plating bath on a set schedule,
but usually twice a month.
COST SAVINGS
The institution of water reduction techniques resulted in
a cost savings of $7,000 the first year. The savings will
undoubtedly be more signigicant in 1981 because of a 26
percent increase in Baltimore water and sewer rates. In
addition to these savings, our cadmium use has decreased.
Before the HSA Reactor was installed, we consistently had
PROCESS FLOW DIAGRAM
HSA METAL RECOVERY SYSTEM
TO RECTtFlCT
Figure 2.
68
-------
HSA
CADMIUM
PLATE
PROCESS
•*
-D-|
CADMIUM
PLATE
PROCESS
TANK
To Central Sump
Fig. 3— Current HSA Reactor System at Allied Metal Finishing.
a cadmium-use-to-sales ratio of 0. 1 3. Since the Reactor was
installed, the ratio has dropped to 0.09 — a 31 percent
reduction in cadmium purchases.
• By reducing treatment chemical needs and sludge
production, the Reactor will be saving even more money
when the Federal pretreatment regulations are enforced.
Sludge disposal is a major concern for us at Allied, because
we are currently paying $1.35 per gallon for disposal of
RCRA-manifested waste. At projected production rates,
these savings will be over $10,000 per year.
SYSTEM MONIRTORING
As I discussed earlier, the Baltimore Department of
Public Works has monitored industrial effluents since 1975.
When the Reactor was installed, the Depatment was invited
to evaluate the effectiveness of the technology in reducing
the cadmium concentration of the effluent. The
Department agreed, and set up monitoring equipment in
March of 1981. The results were phenomenal—the
cadmium concentration in the effluent was 0.432 mg/L.
Most remarkably, this concentration was achieved at the
new low flow rate and during a period of high cadmium
plating production.
The Department of Public Works was impressed with the
results. Since March, the Department has monitored on
two other occasions. The results were 0.28 mg/L and 0.22
mg/L cadmium. The numbers were so low that the
Department began reporting the concentrations on its
official forms in parts per billion rather than in the
conventional parts per million or milligrams per liter.
CONCLUSIONS
The results to date indicate that our decision to use HSA
was excellent. The primary goal of finding a cadmium
control technology to meet current and future demands has
been met. We are now in a position to increase our
cadmium plating volume without environmental worries at
a time when many platers are leaving the market. In
addition, we expect substantial cost savings once the
Federal pretreatment standards have been implemented.
The work described in this paper was not funded by the
U.S. Environmental Protection Agency and therefore the
contents do not necessarily reflect the views of the Agency
and no official endorsement should be inferred.
69
-------
Some Successful Applications of Electrodialysis
William G. Millmam and Richard J. Heller*
Metal recovery from plating solution dragout has become
a prime concern for many metal finishers lately. To satisfy
the demand for metal recovery, many new recovery systems
have been introduced into the market. Electrodialysis (ED)
has been one of the more successful systems introduced over
the past five years. Some of the most successful applications
will be reviewed in this paper.
In order to fully understand the application of
electrodialysis, a brief discussion of the theory follows.
Electrodialysis, in the pure sense, is the movement of ions
through ion selective membranes, under the influence of an
electromotive force (voltage) applied across the membrane
area. Ion exchange membranes are the key to this process
and exist in two basic distinct forms—cationic and anionic.
Cationic membranes allow only the positively charged
ions such as copper, zinc or nickel to pass through them,
while conversely, anionic membranes allow only the passage
of negatively charged ions such as chloride and sulfate, or
cyanide complexes, etc. These membranes are thin sheets of
plastic material which have been subsequently impregnated
to impart the appropriate ionic characteristic. Membranes
then when arranged in parallel cells between two electrodes,
positive and negative, along with specifically designed
spacers and gaskets to separate the membranes into leak-
tight cells, give the basic construction of an electrodialysis
stack.
Figure 1 is a schematic operational drawing of such an ED
stack. At each end are the electrodes, a cathode of stainless
steel and an anode of platinum-clad titanium. Each electrode
is in a cell around which flows a compatible salt solution of
electrolyte whose purpose is to collect and dispel resultant
gases such as hydrogen and oxygen and impart overall
*By William G Millman and Richard J Heller
The Lea Manufacturing Company
Waterbury, CT
electrical conductivity to the stack. Subsequently, there at
number of individual cell compartments of alternating lay
of anionic and cationic membranes. The even numbei
cells are the paths for the feed solution; the feed soluti
being the constantly circulated solution from a dragout
reclaim tank. The odd numbered cells are the collecting,
concentrating, cells in which the concentrated plat
solution is collected for return to the plating tank. 1
cations are the metal ions such as nickel, copper, zinc, t
which are attracted to the left toward the cathode, but c
only move into the next adjacent cell where they ;
prohibited from further migration by an anionic membra
Likewise, the anions such as the chloride, sulfate, etc. i
attracted to the right side, but again are prohibited fr<
further migration by the presence of a cationic membra:
Since the entire system must be electrically neutral, 1
recovered or concentrated solution is collected in the o
numbered cells while the reclaim rinse solution, that
circulated in the even numbered cells, is constantly bei
reduced in metal salt concentration.
Figure 2 shows this process in schematic fashion. This <
going process then is engineered in terms of stack size
remove the same volume of plating solution as is dragged c
of the plating tank into the reclaim tank during the norn
production operation. The remaining components in
operational electrodialysis unit consist of a rectifier
provide the appropriate potential across the two electrod
a pump to circulate the electrode rinse, and a pump and fil
to circulate the reclaim rinse through the ED stack. This th<
along with the appropriate monitoring system and mete
constitutes an operational electrodialysis unit as can be se
in Figure 3.
ED Application in Gold Plating Operations
Circuit-wise
Some of the most successful applications of ED ha
been on gold plating baths. The high conductivity of typii
CONCENTRATE
i I r
A Ic
ELECTRODE
RINSE
M*
ANODE
+
COLLECTION
Fig. 1— Schematic Operational Drawing of ED Stack
DRAG-IN
21/BBL
10 BBL/HR
SOg/IM
1000 g/hr M
!
DRAG-OUT TANK
AVQ CONC
500 PPM M*
CONDUCTIVITY
1500 p. MHOS
FEED
RETURN
ED
UNIT
\
CONCE
1000
NTRATE
8M'
HR
Fig. 2—Schematic of ED Process
70
-------
Fig. 3—Operational ED Unit
solutions has produced gold recovery rates over 99%. We
have found that gold platers are most resourceful in
discovering systems to optimize gold recovery. ED plays a
major role in these systems due to low initial cost, low energy
consumption, and ability to produce a product suitable for
direct recycle to the plating tank.
Circuit-Wise of North Haven, Conn., is one of the larger
printed circuit manufacturers in New England. Before they
decided on a recovery system for their Mircoplate 7000 Tab
Plater, four competing recovery systems were evaluated
both by in-plant engineers and by an independent
consultant firm. Electrodialysis was chosen as the most
applicable process for this installation.
Initially, the ED system was operated on the dragout
rinse following the plating station, and a small ion exchange
column was installed on the second rinse to recover the last
gram of gold. The effectiveness of this system was
demonstrated by atomic absorption analysis (AA) on the
third rinse which had no detectable gold.
The rinsing in this automatic tab plating machine is very
effective and there is very little carryover of contaminants
from one process tank to another. Therefore after analysis,
the concentrate recovered by ED was returned directly to the
plating tank. The system operated in this manner, returning
recovered concentrate directly to the plating tank with no
buildup of contaminants. Over 35 troy ounces of gold were
recovered in the first operation, and with the price of gold at
that time,' the ED system had paid for itself. Additional
savings were building up in the eliminated interest charges
which would result from gold in dead inventory on ion
exchange resin and at the refiners. Refining charges were
also eliminated.
The ED was operated in the constant voltage mode which
allows the concentration of the recovered solution to "float",
but will recover the maximum amount of gold. Operating in
this manner, the concentrate ran from a low of 0.14 troy
oz/gal to a high of 5.26 troy oz/gal.
Circuit-Wise ran for 8 months in this manner, recovering
over 150 troy ounces of gold. Typical gold concentrations in
the recovered solution and amounts of gold recovered are
listed in Table 1. The engineers, encouraged by this
performance, looked for ways to recover additional gold
from their wide range of processes.
The culmination of this research is now operating at
Circuit-Wise. Gold recovery is enclosed in a separate high
security area. Within this room, ED is the heart of the
recovery system.
On the production floor, each gold plating area is
organized with a dragout tank following the plating station.
The second rinse tank is also a dead rinse as is the third
rinse. The first dragout rinse is withdrawn into drums
periodically to maintain the concentraation of gold below
0.1 oz/gal. The second and third rinses are continuously
circulated through separate ion exchange cartridges. When
the concentration of gold in the third tank exceeds a pre-set
level, the resin on the second tank is retired, the ion-
exchange on the third tank is moved to the second, and
fresh resin is installed on the third tank. This system
effectively recovers over 99% of the gold dragout.
Within the recovery area, the drums containing the
dragout solution from each plating line are stored and
segregated as to type of bath. When a sufficient quantity has
been collected, the solution is concentrated through the
ED instrument. Analysis of the stripped solution by AA
confirms the complete removal of gold before being sent to
waste treatment. The concentrate is also analyzed for gold
December 1980
January 1981
February 1981
March 1981
April 1981
May 1981
June 1981
Gold Concentration of
Maximum
concentrate
Troy oz/gal.
4.48
5.26
197
1.86
126
3.04
1.87
Table 1
Recovered Solutions
Minimum
Concentrate
Troy oz/gal.
0.39
0.45
0.16
0.27
0.43
0.28
0.16
From Microplate
Average
Concentrate
Troy oz/gal.
1.22
2.11
0.98
0.98
0.79
1.43
1.01
Troy ounces
Recovered
35.5
18.3
13.0
10.1
15.8
21.4
9.5
71
-------
GCLD CCNCENTRATE
= Counterflow Rin
Fig. 4—Recovery system at artistic plating.
Fig. 5—Rinse purification system at artistic plating.
content and then bottled and placed in stock as
replenishment solution for the individual lines. The
foreman signs out for the recovered solution just as he does
for new products. Very close control is kept over the
recovered solutions. In the first ten weeks of operation, over
180 troy ounces of gold were recycled directly into the
plating tanks. The analysis of these solutions is tabulated in
Table 2.
The savings in interest charges due to immediate recycle
are significant. Even with ,an 8-week return of gold
recovered by ion-exchange or plating out, there would still
be about 150 troy ounces of gold held as unusuable
Analysis of
Lot n
\
1A
2
2A
3
4
4A
5
5A
6
6A
1
7A
8
Table 2
Recovered Solutions— July-Sept. 1981
Volume
63
38
68
54
69
31
32
36
36
30
36
61
54
431
Concentration
1.44
0.556
1.39
0.28
0.92
1.74
0.31
2.23
0.37
3.12
0.55
1.25
0.12
0.98
Troy
ounces
24.0
5.6
25.0
4.0
16.8
14.3
2.6
21.2
3.5
24.8
5.2
20.2
1.7
11.2
180.1
Table 3
Installation Cost
Components
E D System
Pumps
Piping
Controls
Resins/Filters
Installation Labor
Total
Cost
$16,000
700
1,000
1,200
650
1,500
$21,050
inventory in various stages of recovery. At today's high
interest rates, the savings over one year would be over
$13,000.
Circuit-Wise also recovers gold from their rejects. After
stripping the gold, ED is used to concentrate the gold in the
solution to 8 oz/gal for ease of handling and control of gold
content. Gold present in ion exchange resin is recovered as a
solid after burning off the resin.
Artistic Plating Co.
Artistic Plating Co. Inc. is an upper midwestern job shop
specializing in precious metal plating. Of particular interest
Table 4
Annual Operating Cost
Components
Electrical Power
Chemicals
Filter Cartridges
Replacement Membranes
Labor
Resin (Gold Selective)
Resin (H-OH)
Total
Cost
$300
175
150
750
1,000
70
900
$3,345
Table 5
Silver Recovery Justification Oneida Ltd.
Operating conditions Before E.D.
Operating Hours
Dragout
Recovery Method
8 hrs./day
20,000 Troy oz/yr.
Precipitation as
Silver Chloride
Savings With E.D. Recovery
Cyanide Treatment @ 2.60/#
Refining Charges @ $.56/Troy oz.
Interest Charges for Silver at
Refiners - 4 months @ 12%
Annual Interest
Refining Loss 5%
Difference between Oneida's
Assay and Refiners Return
Total Savings with E.D.
Installed Cost of E.D.
$ 5,200/yr
$ll,200/yr
12,800/yr
$16,000/yr
$45,200/yr.
$30,450/yr..
72
-------
Nickel
Dragout
100 ppm Nickel
ELECTRC DIALYSIS
SYSTEM
N>
Concentrate
11 gal/day
7 oz/gal Nickel
Fig. 6—Recovery system at Stratford Metal Finishing.
is the large volume of plumbing hardware which is gold
plated. Seventy percent of their gold consumption is used
on a large assortment of plumbing accessories ranging from
brass and zinc castings to stainless steel stampings to six
foot brass extrusions. Due to the varying nature of the raw
materials received for processing, impurity build-up in
costly gold baths has been a problem of continuing concern.
In the past several years, fluctuations in the cost of raw
materials have been no where more dramatic than in the
precious metal market where changes of up to 100% have
been seen in a matter of months. To combat these problems,
Artistic Plating has designed a system which effectively
eliminates the buildup of bath impurities and maintains in-
house control of all gold recovered.
The closed loop system is designed to recover gold from a
drag-out tank, continuously removing impurities and
allowing reintroduction of gold concentrate into various
baths. It additionally purifies and reuses its rinse water by
means of several techniques common in the metal finishing
industry. The system is unique in that it uses a closed-loop
approach to a plating system generally not thought to be
adaptable to that mode of operation.
The heart of the recovery system is the electrodialysis
recovery system operated on the dragout rinses. The ED
system is piped directly into both the acid gold dragout and
cyanide gold dragout. Only one dragout is concentrated at a
time. The system is equipped to rapidly flush from itself any
residual acid or cyanide remaining before alternating
between dragout tanks. The concentrate is collected and
available for direct recycle into the plating tanks. This may
be seen schematically in Figure 4.
Work being processed in gold plate is rinsed prior to and
after plating in the same closed loop counterflow rinse
station. This rinse station is continually purified by two
separate systems. Organic impurities are removed by
continuous filtration through activated carbon. The second
system provides a high flow to rapidly circulate purified
water for rinsing.
This system is also equipped with a gold selective ion
exchange resin to collect any gold which escapes ED
recovery.
Removal of solids is accomplished by use of a 10 micron
filter. Residual ionic species are removed with an anion-
cation H-OH resin. This procedure is demonstrated in
Figure 5.
The ED unit is operated as required by monitoring
percent conductivity settings on the dragout rinse. The
concentrate from this contains over 95% of all recovered
gold. This concentrate is analyzed and added as required to
gold strike tanks in non-critical, decorative applications,
where the main criteria is the appearance of the plate.
The installed cost of the ED rinse system was $21,050.
The annual operating cost is $3,345. The initial payback
occurred after 9 months of operation. The average gold
recovery rate is 3.9 troy oz/month. Although Artistic
Plating recognizes the cash flow advantages of direct
recycle, they did not directly use this in the payback
justification. The complete figures are tabulated in Tables
3 and 4.
ED Application in Nickel Plating
Stratford Metal Finishing of Winston-Salem, North
Carolina had a serious problem. Their shop is situated over
a stream, and the discharge limits were below 1 mg/1 for all
metals. The shop has been in existence for many years and
the space available for effluent treatment was minimal. In
fact, the available space was so small that they did not have
room to segregate the nickel rinses from the cyanide-
bearing rinses.
This resulted in nickel complexing with the cyanide
giving excessive treatment times, chemical usage, and nickel
in the discharge.
The solution devised by Stratford Metal Finishing was
the treatment of plating rinses to allow recycle of the treated
water for use in rinsing. Although Stratford terms their
water use "closed loop", there is the inevitable discharge of
water to reduce the build-up of dissolved solids.
Occasionally certain solutions such as spent strippers and
floor spills are barrelled and shipped to a licensed hauler.
Electrodialysis plays an important role in the total
effluent treatment package. The only way Stratford could
have made this system functional was to eliminate nickel
mixing with the cyanide in the treatment tanks. They were
not as concerned with the recovery value of the nickel solution,
as in eliminating nickel from their rinses so their recycle
system would work.
The ED was oversized for the amount of nickel dragout
expected. This would allow Stratford to operate the ED in
the constant voltage mode to effect the greatest extraction
of nickel ions from the dragout while allowing the
concentration of nickel in the recovered solution to float.
The concentration of the recovered solution was
unimportant as there was considerable evaporation from
the plating tanks, therefore sufficient room for recycle.
ED Application in Chrome Plating
The chrome plating solutions are also operated in a
"closed loop". A proprietary membrane separation process
is used for the concentration and recovery of chrome
plating solutions. The recovered concentrate is used to
replenish the plating tanks.
Rinses from the cyanide plating tanks are handled by
conventional chemical treatment to oxidize the cyanide and
precipitate the metals. Rinses from the cleaning and pickling
operations are neutratlized by conventional means also. The
entire effluent flow is then passed through a large filter press
to remove solids. The clear effluent is then partially
deionized through the use of an H-OH ion exchange unit
before reuse.
This system does not save any money compared to a
conventional system; in fact it costs more to operate. But the
peace of mind obtainable by being able to cement over all the
drains in the building has been more than worth the
expense to the owners.
73
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Table 6
Silver Recovery at Oneida Ltd.
u ii
II 19
11 24
II 30
12 4
12 10
12 71
Silver (Tr
Dragout
056
050
35
58
44
52
34
o:/gal.)
Concentrate
4 19
80
64
8.2
70
83
57
Potassium
Dragout
.9
3
1
.8
.7
9
.3
Cyanide (ozjgal.)
Concentrate
67
4.5
6.1
6.6
7.4
6.6
8.5
Potassium
Dragout
1.0
0.45
0.55
0.60
0.40
0.45
Carbonate (oz/gat.)
Concentrate
0.47
<.IO
<. 10
CIO
<. 10
<. 10
The description of operation is sure to raise a few
eyebrows among the readers of this paper. This method of
recycle is not being recommended as general practice.
Stratford Metal Finishing was faced with the option of
reducing the metal content in the effluent to virtually
unattainable levels or closing down. They chose a third
option; elimination of all discharge and sealing all the
drains in the building. Hard work, constant attention to
details, and an owner determined to make the system work
have contributed to its success. This example is presented
not as an operating recommendation, but only to
demonstrate how electrodialysis is contributing to successful
recovery and recycle.
In operation, the system consists of a single dragout rinse
following nickel plate continuously purified by ED, followed
by a 1% chromic acid solution as an activator before chrome
plate. Sulfuric acid is added to the dragout tank to maintain
conductivity and allow the greatest recovery of nickel. The
operation is shown in Figure 6. The 1% chromic acid
solution is sent to a licensed hauler about once a month.
This system has been in operation for 6 months. During
this period the average concentration of nickel in the
dragout rinse has been below 100 mg/1. On the average a
nickel solution at 75% of bath strength is recovered at 11
gallons per 16 hour day. There has been no significant drag-
in of nickel or chloride into the chrome plating tank. And
there has been no nickel detected in the effluent treatment
system.
ED Application in Silver Plating
Oneida Ltd. located in Sherrill, New York is a major
manufacturer of silver plated tableware and holloware. As
their production increased due to both increased sales and
acquisition of new product lines, economical recovery of
dragged out silver became a top priority.
The approach taken by the engineers at Oneida Ltd. was
very conservative. After evaluating many systems, the most
promising were installed for on-site evaluation. As a result
of these tests, the equipment justification figures were
revised and electrodialysis was chosen as the most promising
method. The justification breakdown is given in Table 5.
Once the electrodialysis recovery system was instal
periodic analyses were made to determine if the system •
living up to expectations. The results of these w
tabulated in Table 6. The most interesting item reveE
from analyzing this table is the apparent order of recov
of the ionic species.
The major components of a silver bath are silver cyan
potassium cyanide and potassium carbonate (from
breakdown of potassium cyanide). When the drag
containing these chemicals was passed through
electrodialysis unit, the silver cyanide passed through
membrane in a greater proportion to the potassium cyan
than present in the dragout. The potassium carbon*
which is weakly ionized compared to the cyanides, \
recovered in only very small amounts.
The major conclusions that can be drawn from th
results are (1) the silver may be recovered at concentratic
over 2 times bath strength; (2) carbonates do not tend to
concentrated by electrodialysis; and that (3) the recovei
concentrate may be added directly to the plating bath
reuse. Since the dragout is high when plating holloware, I
concentration of the highly conductive cyanide ions
sufficient to block the transfer of the carbonate which 1
been a problem with other direct recycle recovery metho<
Thus the concentrated dragout may be directly recycl
without fear of accelerated build-up of carbonates.
Electrodialysis systems are also operating on palladix
chloride, acid tin (sulfate) and cyanide cadmium. In tot
there are more than fifty operating electrodialysis systei
in the field, and this total is expected to more than double
1982. Systems designed for the recovery of fluobon
solutions and chrome plating solutions are expected to
released from development into full production duri
1982. The wide range of applications and economical cc
have established electrodialysis as the preferred method
recovery for many solutions. The many success)
applications in the field will insure its continued growth.
This paper has been reviewed in accordance with the U
Environmental Protection Agency's peer and administi
live review policies and approved for presentation a,
publication.
74
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Electrolytic Metal Recovery
Comes of Age
C. A. Swank & W. J. McLay*
Electrolytic metal recovery is one of a growing number of
tools available to the metal finisher for recovery of the
materials lost in the dragout from his plating tanks. The
stringent restrictions on the disposal of metal finishing
wastes, and the increasing costs of disposing of sludge
created by the metal in these wastes, combine to make
recovery of the dragout a very attractive proposition. The
most commonly used recovery technologies are:
evaporation, reverse osmosis, electrodialysis, ion exchange
and electrolytic metal recovery. Each of these technologies
has its niche in the field of dragout materials recovery. Two
or more of these techniques may also be used in conjunction
with one another; for example, ion exchange can be used to
concentrate a metal ion from a very dilute rinse stream and
the metal can then be electrolytically recovered from the
more concentrated regenerant.
The first four of these methods of recovery are all
concentrative in nature— they basically remove water, and
varying amounts of impurities, from the dragout and
produce a concentrate that is available for return to the
plating bath. Two problems are inherent in concentrative
methods: bath growth and bath contamination. It is almost
always the case that when soluble anodes are used, the anode
efficiency is higher than the cathode efficiency with the
difference ranging up to very high values for some barrel
plating lines. The resultant metal buildup is usually more
than compensated for by dragout, but when dragout return
is practiced, the increase in metal concentration can become
a significant problem. Plating baths are normally purged of
trace impurities by dragout, but when dragout is artificially
reduced, these trace impurities can build up to significant
levels. The buildup of impurities can be controlled,
however, by the incorporation of purification steps into the
recovery system, and the use of high purity water for rinses
and bath makeup.
Electrolytic metal recovery is radically different from the
other methods of recovery; it is selective, removing only the
metal and thus, decoupling the production and recovery
processes. Since electrolytic metal recovery doesn 't
concentrate the dragout and return it to the bath, a properly
functioning plating bath will continue to give satisfactory
performance after electrolytic metal recovery is put on line.
*C A Swank & W. J McLay
ERC/Lancy
A Dart & Kraft Company
525 West New Castle Street
Zelienople, PA 16063
Electrolytic metal recovery does recover the most valuable
constituent of the dragout—the metal. The metal is also the
component of the dragout that is responsible for the
formation of the sludge.
The choice between electrolytic metal recovery and one
of the concentrative methods of recovery is basically an
economic one. The metal is the most valuable constituent of
the dragout from many plating baths, while the cost of
replacing the other components is not high enough to
warrant the cost of recovering them. In other instances, the
metal is relatively inexpensive, and recovery of the entire
dragout makes more economic sense. Capital expenditures
for the recovery equipment, and the operating costs, must
be considered along with the recovery value of the dragout.
The complexity of the equipment and the skill required of
the operator, as well as the amount of operator time
necessary are also important factors in the decision.
Electrolytic metal recovery is not a new technology. The
mining industry has used electrolytic means of refining ores
for many years, and copper has been recovered from
pickling solutions for a significant period of time. In recent
years there has been considerable, and increasing, interest in •
the use of electrolysis for the recovery of metals from dilute
rinse waters.
Dilute rinse waters pose a special electroplating problem.
The cathode polarization that is the concern of all platers is
a much more acute problem for someone who is trying to
plate out of a very dilute solution. In general, as plating
proceeds, the area of solution next to the cathode becomes
depleted in metal ions, forming a polarized layer. The ions
must diffuse into and across this layer before they can be
plated out. There are fewer ions present in dilute solutions,
so the rate of diffusion into and across the polarized layer is
much slower, and the layer becomes thicker and more
depleted. Severe cathode polarization can lead to poor
quality 'deposits: the formation of dark, powdery, burned
areas and trees that can grow across to the anodes and short
out the cell. The efficiency at the cathode can be greatly
reduced, as the electricity is used to decompose water and
form hydrogen gas, instead of plating out the metal. There
are a number of ways that the problems associated with
cathode polarization can be reduced: by running at a lower
current density, adjusting the chemistry and temperature
of the solution, and agitating the solution.
When plating is carried out at a low current density, the
polarized layer is narrower and metal ions can diffuse into
and across it more easily. For a given amount of metal, the
75
-------
larger the cathode surface area, the lower the current density
necessary to plate out the metal. One way of increasing the
cathode surface area is through the use of a large tank with
many rows of cathodes and anodes. This approach is
cumbersome, at best, and to recover from low
concentration rinse waters, hundreds of pairs would be
needed. A more practical way to achieve high surface area, in
a low volume, is through the use of stainless steel wool or
porous carbon as a cathode. There are companies working
on both of these approaches. It is easy to remove the metal
from dilute solutions this way, but the metal can't be
recovered until it is dissolved out of the cathode into a
concentrated solution and plated out by conventional
methods.
The characteristics of a plating solution can be chemically
altered in a number of ways. The concentration of metal ions
in the solution can be increased and chemical additions can
be made to the solution. For example, electrolytes can be
added to improve the conductivity of the solution and grain
refiners can be added to improve the quality of the deposit.
In addition, when the temperature of a plating bath is
elevated, the metal ions in the solution become much more
mobile and can diffuse much more rapidly through the
polarized layer.
Every plater knows that if he agitates his plating solution
or his cathodes he can either plate at a higher current density
or lower the concentration of metal in his plating bath. Metal
has been electrolytically recovered from waste water
containing as little as 100 ppm of metal with the aid of
rapidly rotating cathodes.
Many of the potentially favorable adjustments that can be
made to an electrolytic recovery system are impractical for
a once through system, but can be taken advantage of if a
closed loop system is utilized. The first rinse after the plating
tank can be isolated and continually recirculated through an
electrolytic metal recovery cell. Since the basic recovery
solution is being reused, it can be heated, the concentration
of metal ions can be allowed to build up to a reasonable level,
and other adjustments can be made to the chemistry of the
solution.
One electrolytic metal recovery system utilizing rapid
agitation of the recovery solution has been used to recover
metals from solutions containing as little as 0.04 ppm of
metal. The solution is recirculated past the electrodes by
impellors located at each end of the cathode compartment.
Impellor design has been optimized to provide a uniform
flow of recovery solution past the surface of the cathodes. In
most cases the reusuable cathodes are of stainless steel, and
are provided with edge guards to aid in the removal of the
metal deposit. The metal produced with this electrolytic
metal recovery cell is of high quality and can either be reused
as the soluble anode in the plating tank or sold. The system is
basically simple to operate, and once the start-up period is
over, requires a minimum of operator time.
Although recovery can be achieved from solutions
containing very low metal concentrations, it is usually
recommended, for economic reasons, that the concentration
of metal ions be kept in the 3-6 g/1 range. When recovering
precious metals, such as gold and silver, it makes sense to use
the extra capacity necessary to maintain the metal
concentration on the order of 50-200 ppm in the recov
rinse. Furthermore, when an electrolytic metal recovery
is used for the recovery of metal from a spent plating b;
the initial metal concentration is high enough that it is oi
economically feasible to reduce the concentration to le1
below 1 ppm.
The electrolytic metal recovery system has b
successfully operated on copper sulfate, gold cyanide, sil
cyanide, tin/lead fluoborate and many other recov
solutions. Laboratory work has recently been completed
the recovery of copper from a cyanide plating solution,
use with a high speed barrel plating operation. Because
the large difference in cathode and anode plat
efficiencies and the large dragout associated with ba
plating operations, a growth in the plating bath was ant
pated if dragout return was practiced, and it was felt thai
electrolytic metal recovery cell placed on the ri
immediately following the plating bath would be a use
component of this plating system. A five week plating i
was done during which dragout to the rinse was simulated
periodically adding small quantities of used copper cyan
plating bath to the solution in the recovery cell. The cop
concentration was maintained at an average of 5 g/1, and'.
grams of copper were recovered during 852 ampere-hour;
plating. The cathode efficiency was 67%, and 82% of
cyanide added to the system was destroyed.
One of the most common applications for electroh
metal recovery is the recovery of copper from sulfuric a
solutions. At a GTE/Automatic Electric facility, coppe
being recovered from the rinse following a pre-etch soluti
Data were collected over a five week period, during wh
536 pounds of copper were recovered. The average cop
concentration was approximately 5 g/1, and the cathc
efficiency was 90%.
Besides being used to recover metal from dilute ri
waters, the electrolytic metal recovery cell can also be usec
recover metal from crystals and sludges, and to regener
process solutions. Data were collected from
GTE/ Automatic Electric facility that utilizes an electroh
metal recovery cell to regenerate a sulfuric acid le<
solution. The copper concentration in the leach solution \
maintained at an average of 2 g/1, and 86 pounds of cop]
were recovered in a week at a cathode efficiency of 96'
Electrolytic metal recovery is one of the most versatile a
valuable tools available to the plater for the recovery
metal wastes generated in a plating shop. It has minir
impact on the production line when it is used for the recov
of dragout, and it can be applied to recovery from otl
areas in the plating shop. Electrolytic metal recovery is i
universally applicable as a recovery technology, but in ma
cases it is the most economical alternative available when 1
metal value is much higher than that of the otl
components of the bath, and when capital costs of i
equipment, operating costs, and time and skill required
the operator are taken into account.
The work described in this paper was not funded by
U.S. Environmental Protection Agency and therefore
contents do not necessarily reflect the views of the Agei
and no official endorsement should be inferred.
76
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New Developments For the Treatment of
Wastewater Containing Metal Complexers
Dr. C. Courduvelis, G. Gallager, & B. Whalen
Several existing technologies are available to treat metal
bearing wastewaters. The simplest, is conventional alkaline
precipitation using caustic or lime. This process is inhibited
by the presence of some complexing agents, which keep the
metal salts in solution. Processes to precipitate metals in the
presence of complexing agents such as insoluble starch
xanthate (ISX), ferrous sulfate, cellulose xanthate,
hydrogen peroxide, sodium hydrosulfite, and sodium
borohydride have been developed. All of these processes
use expensive chemical precipitants, which convert the
metal to a sludge, requiring dewatering and discarding.
We now have developed a process employing ion
exchange resins to remove heavy metals from wastewaters
in the presence of complexers or chelators (U.S. Patent No.
4,303,704). The process has the simplicity, convenience, and
the low cost enjoyed by the water softening processes, and we
expect it to receive wide acceptance in the plating and surface
finishing fields. This development has been delayed because
these specialty resins have only recently been available for
industrial use.
It seemed to reason that a resin with chelating groups
would prefer heavy metals to sodium or a chelator. This resin
could take a metal away from its complexer if the
complexer's chelating or stability constants are less than the
chelating constant of the functional group of the resin. This
led us to prepare resins by reacting polyethyleneimines with
chloracetic acid and cross-link the "comb-like" polymer,
which structurally resembles the powerful chelator EDTA.
-N-CH-CH-N- + CICH.C'OONa - N-CH-CH-N
II l '
H H NaOOCCH* CH^COONa
GE1 •<:
epichlorohydnne
or dibromides
The approach failed. Cross-linking of this highly
hydrophylic polymer created a thick gel, preventing liquid
flow. Soon afterwards, a commercial chelating resin became
available. The resin is a cross-linked polystyrene bearing
iminodiacetic acid functional groups:
C -
CH2COOH
CH2-NX
\CH2COOH
The results were as predicted: Very high efficiency for
'Dr. C. Courduvelis, G. Gallager, & B. Whalen
Enthone, Inc.
New Haven, CT
removing copper from an electroless copper solution.
(Electroless copper contains copper sulfate, a chelator, and a
large quantity of sodium ions.) Under proper conditions the
effluent contains less than 1 ppm of copper, the "free
chelator", and sodium.
The resin is packed in a column and the electroless
copper solution is passed through at an appropriate rate
and pH. The copper is held on the column and the solution
containing the chelator is passed through and can be dis-
carded. After the resin is exhausted it is regenerated with
dilute sulfuric acid which redissolves the copper retained on
the resin. This copper bearing acid solution can be treated
with sodium hydroxide or lime to precipitate the copper
quantitatively into very pure copper hydroxide, or to plate it
out and recycle the acid to be used in the next regeneration.
Another application of ion exchange resins for recycling
the copper and chelator from electroless coppers has been
described by Zeblinski.6
Chelating resins are the only resins which seem effective
for this process. Typically, cation-exchange resins prefer
sodium over a heavy metal. The small amount of heavy
metal which is captured on it is accompanied by its chelator.
Both the metal and the chelator then are dissolved together
Figure 1-1.
. - 33.6 grams total
1000 mis. of sulfuric acid
Figure 1-2.
77
-------
1 »g/l -
COPPER DETECTABLE IN THE EFFLUENT
AFTER PASSING 2.38 LITERS OF
AWMONIACAL ETCH RINSEWATER WITH COPPEI
THROUGH 292 GRAMS OF COMPOUND 8118.
1000 2000 D
Amnoniacal etch rinse wate
pentahydrace; for a total
1. anraoniacal etch tin:
lulfati
:opper
Figure 1-3.
00 1000 ml o£ aulfurtc
Figure 1-4.
a.
C.
in the acid or sodium hydroxide when the resin is
regenerated, making metal precipitation impossible. Anion-
exchange resins have no chemical affinity for heavy metals.
Perhaps with polar interaction a few can tie some heavy
metals. Again, the metal takes its chelator along making
precipitation impossible.
Areas where the process can be applied:
\. Electroless copper.
Pass the water rinses contaminated with electroless
copper through the chelating resin at adjusted pH to
remove the copper before discarding.
Recycle such rinses by recirculating through the
resin to maintain low copper level.
Pass the spent electroless copper solutions and
bailout directly or after plating out the bulk of the
copper.
Etchants of printed circuits containing copper.
Ammoniacal, persulfate or perioxide based etchants
and their rinses.
Electroless nickel.
Both the rinses and spent electroless nickel solution.
Various electrolytic copper or nickel rinses and
solutions.
Types of complexers or chelators that can be present
Besides ammonia a variety of other complexers or
chelators can be present together with the copper or nickel in
the solution to be treated.
a. Copper can be separated from carboxylic acid type
chelators like tartrates, and nickel from citrates,
gluconates, lactates, and cuccinatcs, etc.
b. Copper can be separated from alkanolamines like
tetrakis-(2-hyroxypropyl) ethylenediamine, (quadrol),
tetrakis-(2-hydroxyethyl) ethylenediamine, triethan-
olamine, etc.
No separation of copper takes place in the presence of,
2.
3.
4.
ethylene-diaminetetraacetate (EDTA), nitrilotriacelate
(NTA) and other aminoacid type chelators.
The results appear to agree with the expectation based on
the chelating constants. Thus, the immodiacetic acid group
of the resin with chelating constant K=10IO"S '7| will take
away the copper from quadrol, which has a lower chelating
constant for copper, K=l09: |8) and from tartaric acid,
K=10"
but not from EDTA, K=10
and NTA.
K=lO'-fi("7'.
The efficiency for copper separation from quadrol is
greater in an acidic solution, pH=2.2-7.0, than it is in an
alkaline solution. This can be due to the fact that in alkaline
solutions the quadrol becomes a stronger chelator, as it has
been reported elsewhere.(9)
EXPERIMENTAL DATA
Example I: Electroless Copper
A glass column of 4 cm diameter was charged with 292
grams of Compound 8118* to 30 cm height. A solution of
spent electroless copper containing 11.1 g/lCuSCVSHiO, 25
g 1 NNN'N-tetrakis-(2-hydroxypropyl) ethylenediamine
complexer, 8 g/1 free sodium hydroxide, 14 m 1 of 37%
formaldehyde, and 60 g/1 each of sodium sulfate and
sodium formate was acidified to pH 2.5 by addition of 18 ml
of sulfuric acid per liter and passed through the resin at a
rate of 12 ml/min. The results of the copper removal are
shown in the Figure 1-1.
The various fractions of the effluent contained from 8.3 -
15.6 g/1 of complexer NNN'N'-tetrakis-(2-hydroxypropyl)
ethylenediamine.
The column was rinsed with water and eluted with 4%
volume sulfuric, which was passed at the same rate, 12
ml/min. The results are shown in Figure 1-2.
When made alkaline (pH 9-10), the copper in the eluant
was easily removed.
Example 2:
Continuous Removal of Copper from Electroless Copper-
Rinses - Recycling of the Rinse
The same set up of example 1 was used to remove copper
continuously from a rinse water of 6 liters which was
contaminated by continuous pumping of 0.36 ml /minute of
an electroless copper solution containing 2,375 ppm of
copper. This is a 1:100 scale-down of the operating
conditions of an existing plating on plastics installation. The
continuous removal of the copper was achieved by
continuous pumping of the rinse water through the column
at pH 3.5-4.0. If V is the volume of the rinse passing through
the column per minute and if the V volume looses all of its
copper during passage, then V x G = (0.36) x (2375), where
G is the concentration of the copper in the rinse. Thus G will
remain constant for a given value of V. This G is the
concentration at steady state equilibrium.
We established 43 ppm of copper in the rinse, yielding V
equal to 20 ml/minute as the rate of recirculation.
The system was operated continuously for 6 x 24 hour
days. During this time the rinse was analyzed by Atomic
Absorption Analysis and found to contain between 25 and
35 ppm of copper, while the solution returned from the resin
to the rinse had less than 1 ppm of copper. The experiment
was continued for one more day where the copper level in the
rinse rose to a final 52 ppm and the returning from the
column water had 5 ppm of copper. A total of 3050 ml oi
electroless copper was pumped into the rinse indicating 7.2 g
of copper. Since 6 liters of rinse x 52 ppm = 0.3 grams of
*A chelating resin
78
-------
PRODUCTION AVG, 250,000-500,000 SG,FT,/MON.
WATER FLUSH
10J SULFUR IC-
EFFLUENT
<1 PPM COPPER
45 GAL/DAY WATER
CONCENTRATE
30 GAL/DAY
5-8 GRAM/LITER
Fig. 2-1— Overall Schematic of I.X. Column Operation.
SIMPLIFIED SCHEMATIC OF METALIMINATOR
RESIN SHIFT
LOAD
COLUMN
RESIN SHIFT
-IX]—I
-tXh
REGENER-
ATION
CONCENTRATE
OUTPUT
3 GAL/DAY
1,5 GR/LITER
Figure 2-2.
copper, the column had retained 7.2-0.3 = 6.9 g in 292 g of
resin. The 6 liter volume of the rinse was maintained by
periodic removal of portions of the rinse. Elution with acid
was done as in example 1.
Example 3: Ammoniacal Etch
Rinse water containing 13.4 f>'l CuSO4 • 5H2O fully
complexed with ammonia at a pH of 11.5 was acidified to a
pH of 4.0 and run through the column described in example
1 at 13 ml/min. The effluent fractions had the copper
content shown in Figure 1-3.
The column was eluted with 4% vol. sulfuric acid, yielding
the following as shown in Figure 1-4.
Example 4: Electroless Nickel
Electroless nickel solution containing 9 g/1 Ni, 100 g/1
sodium citrate, 50 g/1 ammonium chloride, 10 g/1 of sodium
hypophosphite at pH 8.3 was passed through the same
column of example 1 at 14 ml/1. The first fraction of 600 ml
had less than 1 ppm of Ni (in this case, 5.4 grams of Ni has
been retained by 292 grams of resin). The next fraction of 200
Table 2-1
Advantages and Disadvantages of Fixed Bed Ion
Exchange Using Compound 8118
Advantage!,
I. Consistent effluent quality of less than I ppm copper.
2. Low space requirements.
3. Low energy costs
4. Columns can be designed to handle a broad range of flowrates.
5. Extremely low treatment chemical costs.
6 When considering equally effective treatment options,
comparatively low capital cost.
Disadvantages
\ Incapable of handling certain chelator systems.
2. Downtime required to regenerate columns unless there is a spare
column
3 Incapable of handling concentrated solutions at high flowrates
4 Column si?e, and therefore cost, is flow and copper concentration
dependent
5. Distributors can become clogged with resin, requiring periodic
cleaning.
Table 2-2
Advantages and Disadvantages of
The METALIMINATOR
A I/vantages
\. Consistent effluent quality of less than I ppm copper.
2. Low space requirements, 2' x 4' x 6.5'.
3 Comparatively low capital cost
4 Extremely low treatment chemical cost
5 Continuous - on line operation
6. Less resm required.
Disadvantages
\. Uncapable of handling certain chelator systems
2. Flow limitations, less than 9 gpm.
3 Lower concentration of copper in the spent regenerant
(concentrate).
4. Access is difficult to distributors when periodic cleaning is required
ml had 3 ppm of Ni and the 3rd fraction of 250 ml had 46
ppm. The column was rinsed with water and eluted with 4%
vol. sulfuric acid. The first 245 ml had about 20 ppm of nickel
and the following fractions, a total of 800 ml', contained the
bulk of the nickel, which varied from 4 to 26 g/1. The tail
fraction of about 500 ml contained a few ppm.
Treatment of the combined eluants with sodium
hydroxide precipitated the nickel quantitatively. The
remaining filtrate had only 0.4 ppm of nickel.
FIELD DATA
Research in the laboratory led to the development of
a patented process utilizing Compound 8118 by which
copper and nickel could be removed from most complexers
in solution. The next phase was to field test this process. The
objective of the field test work was to design a full scale
system utilizing the patented process which could operate
under plant conditions. We wanted to examine the system's
ability to efficiently and effectively remove copper from
chelators in solution. The success of this was determined by a
copper concentration of less than I ppm in the effluent.
Additionally, we hoped the metal that was retained on the
resin could be extracted with a small volume of sulfuric acid,
yielding a concentrated solution. This would facilitate easy
handling of the concentrate. This concentrate could either be
precipitated as a hydroxide or carbonate, or the metal could
be electrolytically recovered.
The first major field application of this process was in 1980
at a large plating on plastics (POP) facility. There was an
79
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effective waste treatment system handling their existing
wastewater, but they were committed to adding electroless
copper plating to their POP cycle. The existing system was
not capable of handling this waste stream. A fixed bed ion
exchange (IX) system using Compound 8118 was designed
and installed to accomplish two purposes: (1) prevent the
chelator in the electroless copper from upsetting the existing
treatment system, and (2) remove the copper in the
electroless copper wastestream to below 1 ppm (mg/1).
Figure 2-1 illustrates the plating bath and rinse tank
arrangement, the input and output from the ion exchange
columns, the volume of regenerant used, and the
concentration of copper in the regenerant.
The rinse tanks were modified to take advantage of
counterflow rinsing. Production was highly variable and
therefore the amount of dragout varied considerably. The
dragout from the electroless copper bath averaged 600 grams
per day (2 shifts per day). The water in the first rinse tank was
constantly pumped through a cartridge filter to the two IX
columns. These columns held seven cubic feet of Compound
8118 each. The influent copper concentration varied
between 100-200 ppm (depending upon production). The
effluent from the column contained less than 1 ppm copper
consistently. This water no longer contained copper but still
retained the "free" chelator, therefore it was not combined
with any other waste streams until after treatment.
As previously explained, the copper was retained on the
resin, the chelator was not. When the ion exchange columns
became exhausted, they were first flushed with fresh water to
displace any chelate-bearing solution that had remained in
the column (the hold-up volume) and then regenerated with
dilute sulfuric acid to remove the copper ions. This
regeneration cycle was initiated by an attendant, and
automatically followed a sequence of steps. The columns
were regenerated during periods of production downtime,
such as the graveyard shift, weekends, etc. Approximately 30
gallons of sulfuric acid were used each time the unit was
regenerated. This produced a concentrated solution with 4-8
grams per liter of copper.
Table 2-1 outlines the advantages and disadvantages of
using this type of system on rinsewater.
In an effort to overcome some of the limitations of the
fixed bed ion exchange system, the search continued for
more suitable hardware. In late 1981 a unique moving bed
system was brought to our attention. The fixed bed IX unit
could only achieve continuous operation by providing a
duplicate column. The moving bed system allowed for
simultaneous sorption and regeneration, permitting
continuous on-line operation. With more frequent
regenerations, the volume of resin required became smaller.
This reduced the capital cost of implementing the process.
Figure 2-2 illustrates the input and output from this fully
automatic, continuously operating IX unit.
The unit was set up to handle the dragout from an
electroless copper bath, plating 1000 square feet of laminate
per day. Dragout was estimated to be 25 grams per day of
copper, and the rinse water flowrate was 4-5 gpm. Fluid is
pumped at 5-6 gpm from a feed tank through the load
column, and exits with less than I ppm copper in the effluent.
At the same time sulfuric acid is introduced into the
regeneration column. The sulfuric solution moves up
through the resin in the column progressively stripping the
copper from the resin. The concentrate output has
approximately 1.5 gram/liter of copper, which can be easily
treated by conventional methods. The copper can be
precipitated as copper hydroxide or oxide, or recovered
electrolytically (or through immersion plating). Both the
rinse water treatment and the resin regeneration continue
until they are momentarily stopped by an automatic timer.
When this happens, the clean resin at the bottom of the
regeneration column is shifted to the load column; and the
contaminated resin at the top of the load column is shifted to
the regeneration column. This procedure takes only seconds.
The unit automatically returns to removing copper from
the rinsewater, and regenerating the copper-laden resin.
Table 2-2 outlines the advantages and disadvantages of
using this with Compound 8118 (now called the
METALIMINATOR).
This process has also been successfully tested on
ammoniacal final etch rinse water, and electroless nickel
rinse water.
REFERENCES
1. R. E. Wing, 10th Annual Mtg. Am. Soc. of Electroplated
Plastics, San Diego, CA, Nov. 16-19, 1977
2. J. E. Hanway and R. G. Mumford, US Patent 4,166,032
3. C. H. Roy, US Patent 3,816,306
4. D. R. Kamperman, US Patent 3,770,630
5. Ventron Corp., Beverly, MA; Technical Bulletin No. 47-
A
6. R. J. Zeblinski, US Patent 4,076,618
7. S. Chaberek & A. E. Martell, Sequestering Agents, John
Wiley & Sons, Inc., New York, NY (1959)
H D. A. Keyert, Talanta, 2, 383 (1959)
9. R. Nesbitt & C. Courduvelis, Proceedings AES 8th
Symposium on Plating in the Electronics Industry, 198'
The work described in this paper was not funded by the
U.S. Environmental Protection Agency and therefore the
contents do not necessarily reflect the views of the Agency
and no official endorsement should be inferred.
80
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Batch Hydrolysis System for the
Destruction of Cyanides in Electroplating Effluents
AES Research Project 53
R. G. W. Laughlin, H. L. Robey, and P. S. Gooderham*
ABSTRACT
AES Research Project 53 investigated the effectiveness of simple hydrolysis for the
destruction of cyanides in electroplating wastewaters. Hydrolysis was accomplished in a
batch system for more concentrated cyanide wastes and in a continuous flow system for
dilute rinse solutions. Cyanide destruction efficiencies of greater than 99.9% were achieved
at temperatures ranging from 150-250° C on a variety of different plating wastes.
As a follow-up to this project, the American Electroplaters' Society is supporting a
commercial demonstration of the batch system. This plant is being built by WetCom
Engineering Ltd. and will be installed and tested at Whyco Chromium Co. Inc. in Thomas-
ton Connecticut, early in 1982.
This paper will summarize the laboratory test results and outline the design of the
commercial scale demonstration unit.
BACKGROUND
Alkaline cyanide baths have found favour in the
electroplating of metals, especially copper, zinc and
cadmium, because of their relatively low cost, ease of
operation, superior plating ability and excellent throwing
power. The wastes generated, however, pose a severe
environmental hazard and strict government regulations
have been established to restrict the discharge of these
wastes.
A variety of processes have been developed for the
treatment of cyanide-containing wastes. Alkaline
chlorination of cyanide-bearing wastes has been the
accepted method of cyanide destruction for about twenty
years. In this process, cyanides are first oxidized to cyanates
and then to carbon dioxide and water. More recently,
processes have been described using ozone1; a combination
of a peroxide and formalin2; a packed-bed electrode3; and a
catalytic conversion process." Drawbacks to these methods
may include high capital outlay, incomplete cyanide
destruction or expensive operating costs for treatment
chemicals.
In late 1977, the Ontario Research Foundation (ORF)
conducted a series of tests on the hydrolysis of cyanides to
ammonia and formate as a method for complete cyanide
destruction without the use of expensive chemicals. Heisse
and Foote5 reported 65% conversion of cyanide to formate
at up to 150° C, ~ 93% conversion at 150° C to 200° C and
essentially complete conversion at temperatures in excess of
200° C. The hydrolysis reaction proceeded as follows:
CN" + 2 H2O - NH3 + HCOCT
*R. G. W. Laughlin, Ph.D, P Eng.
H. L. Robey, P. Eng.
Ontario Research Foundation
Sheridan Park
Mississauga, Ontario, Canada L5K 1B3
P. S. Gooderham, MBA, P Eng.
WetCom Engineering Ltd.
Scarborough, Ontario, Canada M1P 3A9
Batch, semi-batch and continuous-flow pilot plant tests
were performed at ORF on sodium cyanide, cadmium plate
tank waste, copper cyanide plate tank waste and copper
stripping solution at temperatures from 188° C to 275° C.
The minimum destruction of cyanide achieved in 60
minutes was 98.75%. In almost all of the tests at the higher
temperatures, removals of greater than 99.99% were
obtained in 60 minutes.
AES Research Project 53 was initiated to confirm the
findings of these tests and to determine the economic
viability of the process.
RESULTS OF LABORATORY TESTS
A number of cyanide wastes were tested in Project 53,
and a significant difference was found in the rate of
hydrolysis. The process conditions required for removal of
total cyanide to less than 1 mg/L ranged from 200° C and
1.7 MPa (250 lb/in2) to 275° C and 6 MPa(9001b/in2). The
most resistant wastes were found to be spent copper plating
solutions and potassium ferricyanide. Test data for these
wastes are shown in Figures 1 and 2.
Three tests were undertaken on specific wastes from the
plant in which the demonstration unit is to be installed. The
streams tested were as follows: a nickel stripping solution
Cyanide Removal
Table 1
From Nickel
Stripping Solution
at
235° C and 550 psi
Reactor Residence
Time (minutes)
Feed
0
15
30
60
90
120
Total Cyanide
Concentration (mg/L)
Batch Process Continuous Process
50,000
12,000
2,000
300
10
0.2
0.01
300
300
50
10
0.2
0.01
—
81
-------
CN )6 AT 220"C
10 60 80
REACTION TIME (minutes)
Hg. 1—Hydrolysis of Potassium Ferrlcyanlde (from AES Project S3 Final
Report).'
COPPER PLATING SOLUTION
40 6O 80
REACTION TIME (mmut«s)
Hg. 2—Hydrolysis of Copper Plating Solution (from AES Project 53 Final
Report).6
with 60,000 mg/Lof total cyanide; an alkaline descaler with
45,000 mg/ L; and a mixture of the two wastes with about
50,000 mg/L. Batch tests were run on the three streams at
full strength. Continuous flow tests were run on the
individual wastes diluted to 300 mg/L of total cyanide to
simulate rinse solutions. The results of these tests are shown
in Tables 1, 2 and 3. The tables show that acceptable
cyanide levels can be achieved with 2 hours or less residence
time at temperatures of 250° C or less.
Figure 3 shows the performance for nickel stripping
solution at 235° C compared to predicted results from
previous tests on nickel cyanide waste at 230 and 240° C.
The observed results match the predicted results from
previous experiments.
The destruction of cyanide in the hydrolysis reactor
solves one part of the plating waste problem. The other
concern, which must be addressed, is the removal of soluble
metals from the treated solution. The effluent from the tests
on the mixture of nickel stripper and alkaline descaler was
treated by pH adjustment and by adding sodium sulfide.
Metal analyses after the various treatment steps are shown
in Table 4. Although large reductions in the concentrations
of soluble metals were achieved during the hydrolysis
reaction itself, sulfide precipitation was necessary to achieve
acceptable effluent levels of soluble zinc and cadmium.
Investigations of alternate approaches to zinc and cadmium
precipitation are planned during the demonstration project.
The exhaust gas from the hydrolysis of the mixed waste
contained 300 ppm of hydrocarbon (measured as methane).
This hydrocarbon component is most likely formic acid or
ammonium formate produced from the breakdown of
cyanide. The gaseous effluent from the process will be
investigated as part of the demonstration programme.
DESIGN OF THE DEMONSTRATION UNIT
As a follow-up to the laboratory programme, the
American Electroplaters' Society agreed to fund a
commercial demonstration of the batch treatment system,
for high strength cyanide wastes, at Whyco Chromium's
plant in Thomaston, Connecticut. In anticipation of this
demonstration project, the wastes investigated during the
laboratory programme were from Whyco Chromium Co.
Table 2
Cyanide Removal from Alkaline Descaler at
247° C and 600 psi
Reactor Residence
Time (minutes)
Feed
0
15
30
60
90
120
Total Cyanide Concentrations (mg/L)
Batch Process Continuous Process
50,000
12,000
2,300
450
15
0.6
0.02
300
300
60
15
0.5
0.02
Table 3
Performance of Bath Hydrolysis Process on
Mixture of Nickel Stripping Solution and
Alkaline Descaler at 242 °C and 550 psi
Total Cyanide Concentration
(mg/L)
50,000
12,000
2,000
400
30
1.5
0.1
Reactor Residence
Time (minutes)
Feed
0
15
30
60
90
120
82
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Table 47
Effect of Hydrolysis on Soluble Metal Concentrations*
Metal Concentration (mgj L)
Hvdrol \\iis Effluent
Metal
Iron
Copper
Cadmium
Zinc
*Test performed
Detection
Limit
~ 1
~ 0.5
~^ I
~ 0.5
on a 50 50 mixture ol
Hrdrolrsix Effluent
After pH Adjustment
After pH Adjustment to 9,2 and Na^S
Raw Cyanide Solution
4500
3500
2200
800
Hvdrolvsis Effluent
312
075
800
62.5
to 9.2
264
0.6
440
60.0
Precipitation
73
YD
1.2
072
nickel stripping solution and alkaline descaler
Since this unit is to be a demonstration unit, it has been
designed with additional features and an extended range of
operating conditions over what might be anticipated for
day to day commercial operation. It is designed to be
capable of operating at temperatures up to 275° C and
pressures up to 900 psi. These conditions were selected on
the assumption that the unit should be capable of reducing
50,000 mg/L of the most resistant cyanide, e.g. potassium
ferricyanide, to less than 1 mg/L in 2 hours or less. Table 5
shows that 275° C would be sufficient to achieve these rates
of destruction.
The initial design concept was for a batch unit capable of
processing 250 U.S. gallons/day of concentrated liquid
cyanide waste in two batches of 125 U.S. gallons each. The
design was based on all of the wastes being pumpable.
Discussions with Whyco Chromium Co. suggested that one
of their major problem wastes is a solidified cyanide
containing sludge, particularly sludge from the bottom of
the alkaline descaler bath. This is removed from the bath
into 55 gallon drums, where it solidifies. In order that these
solidified wastes could also be treated in the batch reactor,
the reactor design was modified to allow it to accept a 55-
gallon drum. Although the mechanical design of the vessel
is more complex with this feature, it was felt that the
additional versatility for this demonstration project justified
the necessary modifications.
Figure 4 shows a general assembly of the batch reactor
system. In order to completely immerse a 55-gallon drum
plus the immersion heaters used to heat up the unit, a
reactor liquid capacity of 150 U.S. gallons is required. To
account for the volume expansion of water at 275° C of
31.5%, and allowing an additional freeboard of 15%, the
total reactor design capacity was established at 230 U.S.
gallons.
The minimum inside reactor diameter required to
accommodate a 55-gallon drum and the heating coils plus
other reactor internals is 30 inches. The total internal
reactor height from the bottom of the ASM E elliptical head
to the top flange required for the design capacity is 83.25
inches. Other system dimensions are shown on the general
assembly drawing in Figure 4. Other design considerations
are discussed below:
Materials of Construction
The batch reactor and associated valves and piping will
be constructed of type 316 stainless steel for corrosion
resistance. To evaluate potential construction materials for
future applications, the following four corrosion coupons
will be supported in the reactor:
• 304 stainless steel
• 304 L stainless steel
• 316 stainless steel
• mild steel
As part of the process evaluation programme, these
coupons will be inspected after 6-8 weeks of reactor
operation.
Drum Loading System
Loading and unloading of the drums will be
accomplished using an overhead crane and monorail
system. The drum will be manually lifted into a "cradle"
designed to contain the drum and inserted into the reactor.
A stainless steel grid will be placed over the drum to avoid
Table 5
Batch Process Conditions for Treating A
Potassium Ferricyanide or Copper Stripping Solution
Containing 50,000 mg/L Total Cyanide
Operating Temperature Required <° C)
Time at
Temperature
(hours)
1
2
3
4
To Achieve Total Cyanide
in the Effluent of
Less Than 10 mg/L
272
756
247
240
To Achieve Total Cyanide
in the Effluent of
Less Than 1.0 mg/L
280
262
252
245
To Achieve Total Cyanide
in the Effluent of
Less Than 0.1 mg/L
284
266
256
251
83
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Cyanide loss during heat-up
Achieved on present sample
. at 235° C
Predicted at 230° C
Predicted at 240° C
45 60 75
Reaction time, mln
Fig. 3—Hydrolysis of Nickel Stripping Solution Compared to Predicted Fig. 4—Bath Reactor—System General Assembly.
Results from Tests with Pure Nickel Cyanide.
any small plated parts contained in the solidified waste from
"boiling over" into the reactor. The crane and monorail will
lift the drum, position it over the reactor, and then lower it
into position in the reactor.
The drum cradle and top grid, as well as a thermocouple
inserted into the solid waste, will remain in the vessel
throughout reaction.
Process Heating System
To heat the reactor plus the 150 U.S. gallons of cyanide
wastes from ambient to 275° C requires an energy input of
approximately 675,000 Btu. This energy could be
electrically supplied using either external wall mounted or
internal immersion heaters. External heaters are inefficient
and may cause baking of the waste on the inside reactor
wall. Thus, internal immersion heaters were chosen for this
application.
The limiting factor in specifying the power rating of the
immersion heaters was found to be the space available to
physically locate both the heaters and a drum within the
reactor. With this limitation, a heater ouput of 54 kW was
specified. This would supply about 185,000 Btu/ hour which
suggests a nominal heat-up time of 3-'/2 hours.
A number of physical and chemical factors may influence
the heat-up time. The actual heat-up time required will be
determined as part of the demonstration programme.
Introduction of a drum of solidified cyanide waste into
the reactor makes the prediction of heat-up time more
complex. In a liquid phase reactor, one assumes good
thermal mixing and fairly even temperatures in the body of
the liquid waste. In the case of a liquid containing a drum of
solid material, a number of uncertainties must be
considered:
(a) The solubilization characteristics of the solid
waste with temperature are not known. Thus, it is
Fig. 5—Continuous Process Flowsheet.
not known at what point in the heat-up the
predominant heat transfer mechanism changes
from conductive to convective.
(b) The thermal conductivity of the waste is not
known.
Temperature control of the system will be achieved
through a thermocouple mounted in the liquid phase close
to the wall of the reactor, feeding a signal to a controller on
the heaters. This same control system will be used when
either liquid or a drum is being processed. During the
demonstration programme, data on heat transfer in drums
of solidified cyanide waste will be generated by installing a
thermocouple into the centre of the drum. Time/tempera-
ture profiles will be recorded from the output of this
thermocouple. Once the heat transfer process is
understood, this thermocouple will no longer be needed,
and this would not be a feature of subsequent commercial
units.
84
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Cooldown System
The reactor and its contents will be cooled from operating
temperature to ~ 100° C by flashing-off water at the end of
reaction. Steam released will exit the reactor via a manually
controlled valve and pass through a water cooled condenser
as shown in Figure 3. Approximately 40 U.S. gallons of
water must be evaporated to remove the necessary heat from
the system.
A cooldown time of 30-60 minutes is expected.
Ammonia Letdown System
Every mole of cyanide that is destroyed produces one
mole of gaseous ammonia. Assuming that this ammonia
does not completely react with water to form ammonium
hydroxide, the gas will have to be vented during reaction.
This will be accomplished in the batch demonstration unit by
an automatic pressure control valve.
The maximum flowrate through this valve depends
heavily on the amount of gaseous ammonia that is actually
released from the aqueous phase, and the amount of water
vapour that is stripped by the ammonia gas. Because of the
uncertainties outlined previously, the valve has been designed
very conservatively, based on our worst experience in
laboratory batch scale tests. A more accurate determination
of the ammonia released in the reaction will be an important
part of the demonstration programme.
Reactor Pressure Relief System
The reactor pressure relief system consists of a rupture
disc (set at 925 psig) and a relief valve (set at 900 psig)
connected in series. The logic of this is as follows: If the
pressure rises to 925 psig, the rupture disc will "crack", and
the pressure will drop rapidly to 900 psig, and will be held at
this by the pressure relief valve. The approach prevents a
complete evacuation of the vessel contents.
PROCESS DEMONSTRATION PROGRAMME
The start-up of the batch demonstration unit is scheduled
for January February, 1982. Tasks to be undertaken during
the demonstration phase of the programme include:
• comparison of full scale performance predicted by
laboratory tests and actual full scale performance.
• confirmation of post treatment requirements (via
pH adjustment, heavy metals removal, etc.).
• examination of corrosion coupons to evaluate
potential construction materials for future
commercial applications.
• evaluation of reactor heat-up time with both liquid
and solid feeds.
• performance of mass balances on the process to
define more accurately liquid loss during reaction.
FUTURE WORK
The batch reactor is best suited to relatively low flow, high
concentration wastes. The other problem facing the plating
industry is high flow, low concentration rinse waters. This is
be,st treated in a continuous flow system. A planned
extension of the present work is to design, construct and
operate a continuous flow demonstration unit for the
treatment of dilute cyanide wastes.
A continuous process flowsheet is given in Figure 5.
In future applications where a batch scale system is
desired, the drum processing feature may not be required. In
this case, loading and unloading of the reactor will be done
by simple liquid transfer pumps.
Automation of the batch process would be a desirable
feature for a liquid cyanide treatment system. An automated
cycle for the operation of the batch system would be as
follows:
• automatic loading of the reactor
• automatic heat-up to the selected operating temp-
erature
• maintenance of the operating temperature and
pressure for a specified period of time
• automatic reactor cooldown
• automatic discharge of the reactor contents
• automatic shut off.
ACKNOWLEDGEMENTS
The authors thank the American Electroplaters' Society
for their support of this most interesting Research and
Development Project. They also thank the AES Project 53
committee, particularly Jack Hyner, Scotty Thomas and Bill
Toller, for their help, encouragement and guidance
throughout the programme.
REFERENCES
1. Bollyky, L. Joseph, "Ozone Treatment of Cyanide-
Bearing Plating Waste". U.S. Environmental Protection
Agency Report EPA-600/2-77-104, Cincinnati, Ohio,
June, 1977.
2. Lawes, B. C., Fournier, L. B., and Mathre, O. B., "A
Peroxygen System for Destroying Cyanide in Zinc and
Cadmium Electroplating Rinse Waters". Plating 60, 902
(1973).
3. Chen, D. T., and Eckert, B., "Destruction of Cyanide
Wastes with a Packed Bed Electrode". Plating and
Surface Finishing 63 (10), 38 (1976).
4. Jola, M., "Destruction of Cyanides by the Cyan-Cat
Process". Plating and Surface Finishing 63 (9), 42 (1976).
5. Heise, G. W., and Foote, H. E., "The Production of
Ammonia and Formates from Cyanides, Ferrocyanides,
and Cyanized Briquets". The Journal of Industrial and
Engineering Chemistry 12 (4), 331 (1920).
6. Cadotte, A. P., and Laughlin, R. G. W. Final Report
P-3083/I AES Project 53 Extension for The American
Electroplaters' Society, November 20, 1980.
7. Cadotte, A. P., Laughlin, R. G. W., Robey, H., and
Cobb, D. Plating and Surface Finsihing, November,
1981, pp 63-65.
Tire work described in this paper was not funded by the
U.S. Environmental Protection Agency and therefore the
contents do not necessarily reflect the views of the Agency
and no official endorsement should be inferred.
85
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Renovation of Electroplating Rinse
Waters with Coupled-Transport Membranes
W. C. Babcock, E. D. LaChapelle and R. W. Baker*
ABSTRACT
A new membrane process is described that can be used to recover plating chemicals
from electroplating rinse waters. The process, called coupled transport, is based on
liquid membranes that are comprised of a thin, polymeric microporous support
containing a metal-ion complexing agent within the pores. Metal ions present in the
rinse solutions are transported across these membranes and can be concentrated into a
relatively small volume. The results of a small-scale field test are presented in which
hollow-fiber coupled-transport membranes were used to recover chromium from
chrome-plating rinse waters. The results of a 125-day test are used as the basis of an
economic analysis that predicts a 1.7-year payback period for a full-sized coupled-
transport unit.
INTRODUCTION: THE USE OF MEMBRANES IN
THE TREATMENT OF ELECTROPLATING RINSE
WATERS
Electroplating rinse waters are dilute solutions of plating
chemicals that result from dragout of the chemicals from the
plating bath into the rinse baths. The discharge of these rinse
waters not only creates pollution problems, but also results in
a loss of valuable chemicals. Current processes for treating
the rinse waters involve precipitation of the toxic
components (mostly metal ions) as a sludge. These sludges
must then be disposed of in hazardous waste sites, where
they remain as a threat to the environment. There is little
doubt that in the future the favored processes for rinse water
treatment will be those that permit recovery of the plating
chemicals in a reusable or valuable form Several membrane
processes fall into this category
The major composition of electroplating rinse waters are
metal ions such as Nf"", Cu+*. and Cr:O~. The ions can be
recovered from the rinse solutions and concentrated using
basically the two types of membrane separation processes
shown in Figure I. In the process in Figure la, a membrane is
used that is permeable to water but impermeable to ions.
Thus, when water flows through the membrane the rinse
water becomes more concentrated in ions and reusable rinse
is produced on the opposite side of the membrane. The only
such process that has been used for treating electroplating
rinse waters is reverse osmosis. In reverse osmosis, water is
forced through the membrane by pressure on the upstream
*W. C Babcock
E D LaChapelle
Bend Research, Inc
Bend, Oregon
R W Baker
Mt. View, California
side—typically about 400 psi.
In the process shown in Figure Ib, the membrane is
permeable to ions but impermeable to water. In this case, as
ions permeate the membrane the rinse water becomes more
dilute and a concentrated solution of ions is produced on the
opposite side of the membrane. Several such processes are
currently being considered for treating electroplating rinse
waters. These include electrodialysis, for which the driving
force to concentrate metal ions is derived from an electric
field imposed across the membrane, and Donnan Dialysis
and coupled transport, in which the energy for concentrating
the metal ions is derived from the flow of other types of ions
across the membrane.
Of the membrane processes with potential for treating
electroplating rinse water, reverse osmosis is the most highly
developed due to extensive research and development over
the past 20 years to apply the process to water desalting.
And, although reverse osmosis has been used to a limited
extent in the electroplating industry, it has inherent
drawbacks that may prevent its widespread use. Foremost
Rinse
Water
Fig. 1—Two Methods of Treating Electroplating Rinse Water with Membranes
86
-------
among these drawbacks is the fact that the membranes are
readily fouled either by suspended matter in the rinse baths
that is filtered out by the membrane or by dissolved
components, such as metal hydroxides, that precipitate on
the membrane as the rinse solution is concentrated. Fouling
necessitates frequent membrane cleaning and shortens
membrane lifetime, leading to high operating costs. A
second limitation is that reverse-osmosis membranes are
chemically degraded by solutions of extreme pH or
oxidation-reduction potential, thus preventing their use with
rinses from common plating operations such as acid copper
or chrome.1" Finally, reverse osmosis cannot in general be
used to concentrate plating chemicals back to their
concentrations in the plating bath because either 1) the
osmotic pressure of the plating bath is higher than the
operating pressure or 2) the membrane is not sufficiently
selective for water over plating chemicals to produce reusable
water when the rinse is concentrated to plating bath
strength.121
Some of the limitations of reverse osmosis can be
potentially overcome by coupled transport, which is a
membrane process of the type shown in Figure Ib. For
example, since there is no fluid flow through the membranes,
fouling by filtration of suspended matter does not occur.
Furthermore, since the process is not pressure-driven, the
concentration of plating chemicals that is achievable is not
limited by the osmotic pressure of the concentrate. Finally,
coupled-transport membranes will withstand relatively
harsh chemical environments such as those encountered in
treating chrome-plating rinses.
COUPLED TRANSPORT
Description of the Process
Coupled transport membranes consist of an organic,
liquid complexing agent held by capillarity within the pores
of a microporous membrane. Metal ions are transported
across the membrane as neutral complexes and can be
"chemically pumped" from a dilute aqueous solution to a
concentrated aqueous solution by the coupled flow of a
second ionic species.
The process is illustrated in Figure 2, which shows coupled
transport of dichromate ion and hydrogen ion with a tertiary
amine (RiN). On the left side of the membrane, designated as
the feed side, dichromate ion plus hydrogen ions are
extracted via the reversible reaction
Cr2O7=
) - (RjNH)2 Cr2O7
(1)
dichromate ion is favored at the low pH of the feed solution.
The amine-dichromate complex then diffuses to the opposite
side of the membrane, designated as the product side. The
pH of the product solution is high, leading to the reverse
reaction in Equation 1. Chromic acid is released to the
product solution and the free amine is regenerated. In the
product solution, dichromate ion is converted to chromate
ion via the reaction
•2Cr(V+3H20-
(2)
Here, (aq) and (org) refer to species soluble only in the
aqueous and organic phases, respectively. Extraction of
The mechanism in Figure 2 leads to the flow of chromium
from a dilute feed solution to a concentrated product
solution as hydrogen ions flow from a feed solution of low
pH to a product solution of high pH. This process can be
used to remove chromium from chrome-plating rinse
waters, where it is present as chromic acid, and to
concentrate it into a small, easily manageable volume.
A similar process that can be used to concentrate cations
such as copper ion is shown in Figure 3. In this case,
complexing agents such as /3-diketones and oximes
(designated RH in the figure) carry the metal ion in one
direction and hydrogen ions in the opposite direction. Metal
cations are chemically pumped from a dilute feed solution to
a concentrated product solution by the coupled flow of
hydrogen ions in the opposite direction, from a solution of
low pH to one of high pH. Processes such as that for
dichromate ion, in which the ions flow in the same direction
across the membrane, are called co-transport; those in which
the ions flow in the opposite direction, such as with copper,
are called counter-transport. Both processes have been studied
extensively on a laboratory scale (3~10) but have not as yet
been used in commercial applications.
Laboratory Demonstrations of the Process
To demonstrate the concepts of co- and counter-
transport, the results of laboratory experiments with
chromium and copper are presented. In these experiments
coupled-transport membranes with 20 cm2 of area were
placed between the two compartments of permeation cells.
These cells have been described in detail previously.'6'
During an experiment, one compartment contained 100 ml
of feed solution and the other compartment contained 100
ml of product solution. The coupled-transport membranes
consisted of a microporous polypropylene membrane,
Celgard 2400 (Celanese Plastics Co., Greer, South
Carolina) impregnated with diluted complexing agent using
methods described elsewhere.16'9)
The results of experiments with chromium are presented in
F\g. 2—Coupled Transport of Chromium Across a Liquid Membrane
Feed Soluti
Product Solutlo
Completing Agent
2RH
•8 Cu
High H Concentrati
- Cu++
Fig. 3—Coupled Transport of Copper Across a Liquid Membrane
87
-------
Chromium
Concentration
(g/L) 2
0
0 10 20 30 40 50 60
2.5
2.0
Copper
Concentration
(g/D 1.0
0.5
0.0
20 40 60 80
Time (hours)
100
Fig. 4—Chromium Concentration in the Feed Solution as a Function of Time
Figure 4, and those for copper are in Figure 5. These are
plots of the metal-ion concentration in the feed solution vs.
time. Because metal ions are transported out of the feed
solution, the concentration decreased.
In the chromium experiment, metal ions were transported
from the feed solution (initially 5 g/L) to a concentrated
product solution. At the completion of the experiment, only
16 ppm chromium remained in the feed solution, with
about 155,000 ppm in the product solution. This represents a
concentration factor of 155,000/16 = 9700. It should be
noted that, from a practical standpoint, co-transport of
chromium from a chrome-plating rinse solution would result
in a concentrate of sodium chromate. Although this
concentrate cannot be returned directly to the plating bath, it
represents a valuable product that could be used in other
metal-finishing processes such as cleaning or etching, or
perhaps in other industries (e.g., for leather tanning).
In the experiment with copper, a synthetic acid-copper
plating solution was used for the product solution. This
solution was diluted by a factor of 40 to represent a rinse
solution and was used for the feed. Copper was transported
across the membrane from the feed to the product solution,
indicating that counter-transport could be used to recover
copper from rinse solutions by circulating the plating
solution on the product side of the membrane. Thus, copper
would be returned directly to the plating solution for reuse.
Process Scale-Up with Hollow-Fiber Modules
For practical applications of coupled-transport, the way
Fig. 5—Copper Concentration in the Feed Solution vs. Time
in which the membranes are modularized will have a strong
bearing on both the operation and economics of the process.
One possible design would be a simple plate-and-frame
module using the microporous polypropylene membranes
used in our laboratory test cells. However, plate-and-frame
units are unlikely to be the optimum membrane
configuration for large-scale plants because of their relatively
high cost per unit area. We believe that hollow-fiber
membrane modules represent an economical module
configuration, and we have developed hollow-fiber modules
such as that shown in Figure 6.
The microporous fibers in these modules are made of
polysulfone, a chemically resistant thermoplastic. A cross
section of a typical fiber is shown in Figure 7. During module
operation, feed solution flows through the fiber lumens and
product solution flows along the outside of the fibers. The
organic complexing agent is held in the porous fiber walls
and metal ions are transported from the lumen to the outside
of the fiber.
Field Tests on Chrome-Plating Rinse Water
Field tests were performed with a small hollow-fiber unit
equipped with two modules having about 15 ft2 of mem-
brane area each. The tests were performed at a decorative
chrome shop that utilizes a three-rinse counter-flow system,
and the unit was installed to treat solution from the first
rinse, as shown in Figure 8. In this configuration, coupled
transport is used to maintain the concentration of the first
rinse solution at a value that leads to adequate rinsing when
Concentrate
Concentrate
End Plug
Rinse -
Solution
Rinse Solution
Partially
Depleted of
Plating
Chemicals
Shell
Hoilow-Fiber
Membranes
Fig. 6— Diagram of a Hollow-Fiber Module
88
-------
Fig. 7—Scanning Electron Photomicrograph of a Polysulfone Fiber (Cross
Section)
Fig. 8—Treatment of Chrome-Plating Rinse Water with Coupled Transport
Rg. 9—Hollow-Fiber Coupled-Transport Unit in Plating Shop
the counter-flow of rinse water is equal in volume to the
evaporative loss from the plating bath. A photograph of the
unit in the plating shop is shown in Figure 9.
The chromium concentration in the first rinse and in the
sodium chromate concentrate produced by the coupled-
Chroniiui
in cht-
Rinst
(ppni)
ooco
Rg. 10—Results of a Field Test Showing the Concentration of Chromium in
the Rinse Solution and In the Sodium Chromate Concentrate vs Time
transport unit are shown for a 125-day test in Figure 10.
During this test, chromium was concentrated between 150-
and 500-fold, with the concentrate containing on the average
of about 6 wt% chromium.
In addition to monitoring the chromium concentrations,
we also determined the chromium flux, which is the rate at
which chromium is transported across the membranes. The
flux of a permeant is a key factor in the economics of all
membrane processes; in general, the higher the flux, the
better the process economics. For the 125-day test in Figure
10, the flux was about 5 Ib of chromium per square foot of
membrane per year (5 Ib/ft2-year). A second test was also
conducted with modified modules that yielded fluxes of
about 20 Ib/ft2-year. However, performance of these
modules deteriorated after only about 50 days of
operation. We are currently engaged in further development
of these high-flux modules to improve their long-term
performance.
PROCESS ECONOMICS
Although coupled transport is still in the developmental
stage, it can be shown that the process potentially offers
extremely favorable economics compared with other
chromium recovery technologies, such as distillation or ion
exchange. The economic analysis presented here is modeled
after a similar analysis performed by the EPA on distillation
and ion-exchange units that recover approximately 5000
Ib/year of chromium."" The objective of the analysis is to
predict a payback time on invested capital for a treatment
system based on 1) the value of the chromium recovered, and
2) the savings in the costs of chemical precipitation and
disposal of the sludges that result from current methods of
treating rinse waters.
For the purposes of comparing coupled transport with
distillation and ion exchange, we have estimated the costs of
coupled-transport units that will recover 5000 Ib/year of
chromium. As shown in Table I, two units were considered:
one with 1000 ft: of membrane area and one with 250 ft: of
membrane area. The larger unit would be required with
89
-------
Table 1
Economics of Two 5000-lb/year
Coupled-Transport Units
Unit Size
Installed Cost
Annual Operating Costs
Deprecation (20C<)
Chemicals
Module replacement
Labor
Annual Savings
Chromium recovered as
Na:CrOj(~ 16,000 Ib yr)
Savings in precipitation
& sludge disposal
1000 ft2
$10,000
2,000
2,000
1,500
700
250 ft2
$4,500
900
2.000
400
700
6,200
4,000
9.000
13.000 13.000
4.000
4,000
9.000
Net Savings = Annual Savings
- Operating Costs 6.800 9.000
Net Savings After Tax
(460; Bracket) 3 700 4.900
Cash Flow from Investment =
Net Savings After Tax +
Depreciation 5,700 5.800
Payback period =
Total Investment
Cash Flow 1 7 years 0.8 years
chromium fluxes of 5 lb/ft:-year, which is the flux we
obtained with our most reliable modules; the smaller unit
could be used if the modules that yield fluxes of 20 lb/ft2-
year are developed further.
The installed costs of these units are estimates based on the
manufacturing costs of several hollow-fiber units we have
constructed plus approximately a 40% mark-up to cover
marketing distribution, and profit. The major annual
operating costs are depreciation, chemicals, module
replacement, and labor. The only chemical cost for the
process results from use of sodium hydroxide in the
conversion of chromic acid to sodium chromate. To recover
5000 pounds of chromium, approximately 8000 pounds of
sodium hydroxide are required and bulk prices of sodium
hydroxide are about $0.25/lb.(12) For module replacement
costs we have assumed a lifetime of 2 years and a module cost
of $3.00/ft2 of membrane. Again, module costs are based on
our estimated manufacturing costs plus a mark-up. A 2-
year lifetime is assumed to be possible based on long-term
laboratory tests with the lower-flux modules that have
currently run 500 days. Labor costs are expected to be low,
and as a rough guide we have used the same labor costs as^
those for similarly sized distillation and ion-exchange units.
Because the sodium chromate cannot be returned directly
to the plating bath and may need further processing and
shipping, we have taken a credit of only $0.25,'Ib, which is
less than half the current bulk price of $0.55'lb.":' For the
annual savings in precipitation and sludge disposal costs we
have used the same savings as used in the EPA analysis of
distillation and ion exchange: ~$1.80/lb of chromiui
recovered."11
The estimated payback periods are short for both un
sizes, with the smaller unit having a payback period of le:
than one-half that of the larger. This shows the incentive t
develop high-flux modules. The calculated payback perioc
for similarly sized distillation and ion-exchange units are 7,
years and 5.2 years, repectively,11" showing that, if lull
developed, coupled transport would offer an economic;
alternative to these processes.
ACKNOWLEDGMENTS
We wish to acknowledge the Office of Water Researc
and Technology of the U.S. Department of the Interior fc
their support in this work.
REFERENCES
1. Crampton, P., R. Wilmoth, "Reverse Osmosis in th
Metal Finishing Industry," Metal Finishing (Marc
1982).
2. McNulty, K. and J. Kubarewic, "Field Demonstratio
of Closed Loop Recovery and Zinc Cyanide Rins
Water Using Reverse Osmosis and Evaporation,
Proceedings of a Conference on Advanced Pollutioi
Control for the Metal Finishing Industry, Kissimmee
Florida (February 1979).
3. Bloch, R., "Hydrometallurgical Separations by Solven
Membranes," in Membrane Science and Technology
J. E. Flinn (ed.). Plenum Press, New York, New Yorl
(1970) pp. 171-187.
4. Schultz, J.S., "Carrier-Mediated Transport in Liquid
Liquid Membrane Systems," in Recent Development,
in Separation Science, Vol. Ill, N.N. Li (ed.). CR(
Press, Cleveland, Ohio, 1977.
5. Cussler, E.L., Multicomponent Diffusion, Elsevie
Scientific Publishing Co., Amsterdam, 1967.
6. Baker, R.W., M.E. Tuttle, D.J. Kelly'and H.K
Lonsdale, "Coupled Transport Membranes I: Coppei
Separations," J. Membrane Sci. 2 (1977) 213.
7. Largman, R. and S. Sifniades, "Recovery of Coppei
(II) from Aqueous Solutions by Means of Supportec
Liquid Membranes," Hydrometallurgy, 3(1978) 153.
8. Lee, K.H., D.F. Evans, and E.L. Cussler, "Selective
Copper , Recovery with Two Types of Liquid
Membranes," AlChE J., 24 (1978) 860.
9. Babcock, W.C., R.W. Baker, E.D. LaChapelle, and
K.L. Smith, "Coupled Transport Membranes. II. The
Mechanism of Uranium Transport with a Tertiary
Amine,"/ Membrane Sci., 1 (1980) 71-87.
10. Babcock, W.C., R.W. Baker, E.D. LaChapelle, and
K..L. Smith, "Coupled Transport Membranes. III. The
Rate-Limiting Step in Uranium Transport with a
Tertiary Amine," J. Membrane Sci., 7 (1980) 89-100.
11. U.S. Environmental Protection Agency,
Environmental Pollution Control Alternatives:
Economics of Wastewater Treatment Alternatives for
the Electroplating Industry. Report No. EPA 625/5-
79-016, Industrial Environmental Research
Laboratory, Cincinnati, Ohio (1979).
12. Chemical Marketing Reporter, Schnell Publishing
Company, Inc., March 22, 1982.
The work described in this paper was not funded by th<
U. S. Environmental Protection Agency and therefore th>
contents do not necessarily reflect the views of the Agency
and no official endorsement should be inferred.
90
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The Application of Donnan Dialysis
To Electroplating Washwater Treatment
EPA/AES Research Project 60
Henry F. Hamil*
Abstract
The operation of a Donnan diafyzer as a means of removal of ionic contaminants from
electroplating washwaters is discussed. The application of both onion-exchange and cation-
exchange membranes for treatment of waste streams from various metal plating lines is
considered. The on-going development of a field prototype Donnan diafyzer for removal of
complex metal-cyanide onions from cyanide bath process washwaters is discussed.
DISCUSSION
Ion-exchange resins are of utility in separation processes
because they can be used to remove ions from dilute
electrolyte solutions. When contacted with a stripping
solution of the proper concentation, the resins release the
ions. If ion-exchange resins are in membrane form, they can
be in contact with the dilute electrolyte solution and the
stripping solution simultaneously, and the ion-exchange
process can be continuous rather than cyclic. This ion-
exchange membrane process is based on the Donnan
equilibrium principle (1) and requires no electrical current or
high pressure for operations, as would be required for
Cation -Exchange
Membrane
Cu+ + Enriched
Effluent
ci— •
0.07M HCi
Fig. 1—Mechanism of Donnan Dialysis.
Cu + + Depleted
Effluent
Cu+
•ci—
0.001MCuCI2
*Henry F. Hamil
Southwest Research Institute
6220 Culebra Road
San Antonio, Texas 78284
electrodialysis or reverse osmosis. This process was first
called Donnan dialysis by Wallace (2).
If solutions of two electrolytes are separated by a cation-
exchange membrane, the anion composition of the two
solutions must remain constant since the membrane is
impermeable to anions. The cations, however, will
redistribute between the two solutions until equilibrium is
reached. This is shown in Figure 1, where the two solutions
are 0.07M HCI and 0.001M CuCl2, respectively. Due to the
high concentration of HCI relative to the concentration of
CuCh, there is an immediate flow of hydrogen ion across the
membrane. Because the chloride ion cannot cross the
membrane, there is a resultant loss of electroneutrality in the
acid solution, and a charge potential builds across the
membrane which is opposite in direction to the
concentration potential gradient. This charge potential
provides the driving force to transfer cupric ions from the
feed across the membrane into the stripping solution. This
process continues until the system comes to equilibrium.
Donnan (1) showed that this equilibrium could be described
by the generalized equation shown in Figure 2. By
c^.-i
(C ^ J
1
z
= K
for any mobile cation i of valence Z, where K is the same
constant for all cations in the system
Fig. 2—Donnan Equilibrium Equation.
[Hi,
*n
]
Fig. 3—Donnan Equilibrium Conditions.
91
-------
Cation-Exchange
Membrane
9 Liters
0.001 MCuCI2
O.OOM HCI
1 Liter
0.072M HCI
O.OOM CuCI2
INITIAL CONCENTRATIONS
CuCl2
HCI
HCI
CuCI2
INTERMEDIATE CONCENTRATION PROFILES
0.0024M HCI
0.00002M CuCl2
0.054M HCI
0.0088M CuCI2
EQUILIBRIUM CONCENTRATIONS
Fig. 4—Removal of Cud: from a Dilute Solution by Donnan
DMytni.
where C0 - initial concentration
C - concentration at time t
t - time, min
k - rate constant, min"'
Fig 8-Metal R«t
I Rate Constant.
application of this equation to the present example, th
equilibrium conditions can then be described by the equalit;
shown in Figure 3.
For a system in which the volume ratio of feed to strippinj
solution is nine, the initial and calculated final equilibriun
concentrations are shown in Figure 4. Ninety-eight percen
of the cupric ion would be transferred across the membrane
and the copper in the stripping solution would bf
concentrated by a factor of 8.8 compared to the initial feec
concentration.
Southwest Research Institute became interested ir
Donnan dialysis about five years ago as a result of a
continuing research program on preparation ol
permselective membranes by radiation initiated graft
polymerization. By using this preparative technique, we were
able to prepare both anion- and cation-exchange
membranes having controlled levels of ion-exchange
capacity and hydrophilicity.
Initial studies to evaluate the performance of such
membranes in Donnan dialysis were conducted in an in-
house research program (3). A simple dialysis system
consisting of a flat membrane, thin channel dialysis cell, two
recirculation pumps, and two reservoirs was used in these
initial evaluations. The feed and stripping solutions were
circulated through the system and samples of each solution
were periodically taken and analyzed for the metal of interest.
The results obtained using a strong acid ion-exchange
membrane to remove various metal cations from an aqueous
feed stream are shown in Figure 5. As can be seen, very high
percentage removal was obtained for all six metal cations,
and the cations were concentrated approximately
twentyfold in the stripping solution. Examination of the data
also indicated that the rate of metal ion removal was
proportional to the metal ion concentration in the absence of
boundary layer effects which were minimized by high
solution flow velocities through the thin channel cell halves.
The rate of metal removal was found to follow a first order
rate equation, allowing calculation of a metal removal rate
constant as shown in Figure 6.
Since some metals are electroplated from cyanide baths, a
series of experiments were also conducted in which removal
of metals as their complex cyanide anions was accomplished
using a strong base anion-exchange membrane. The results
of these experiments are shown in Figure 7. As was the case
with the metal cations, high percentage removal of all four
Metal
Ion
Figure 5
Removal of Metal Cations from Water Via Donnan Dialysis
Feed cone., ppm
Initial Final
Removal
Rale Constant,
Metal Removal
Concentration*
Factor
or
Cu"
Ni"
Zn"
Mg"
Fe"
34.2 0.1
27.3 <0.05
34.6 0.1
32.3 0.1
12.2 0.1
46.5 0.2
* Final conemraiton in stripping solution/initial concentration
Cell Parameters:
Feed Volume
Stripping Solution Volume
Recirculation Flow Rate
Run Duration
99.7
100.0
99.7
99.2
6.3
6.5
5.5
56
99.2 5.6
99.6 5.4
in feed membrane: polyethylene-g (polystyrene-co-divinyl
6 liters
0.3 liters, 0 57N NaCl
425 mL/ min
4 hours
18.9
19.8
18.1
19.4
19.4
18.3 j
benzene) sulfonic acid
92
-------
Figure 7
Removal of Metal-Cyanide Complex Anions
Via Donnan Dialysis
Metal Feed cone., ppm
Ion Initial Final
Ag 50 2 0.3
Cu 48 2 0.2
Cd 51.3 O.I
Zn 46 4 0 3
<"<
Removal
994
996
998
from Water
Rate Constant,
Metal Removal
win-'
4.8
38
4.1
99 4 3.7
* Final concentration m stripping solution initial concentration in feed membrane polyethylene-g[pol\ (N-meth\l-4-vin\lp\nd
Cell Parameters Feed Volume
Stripping Solution Volume
Recirculation Plow Rate
Run Duration
6 liters
0 3 liters. 0 5M NaCI
425 mL, mm
4 hours
Concentration*
Factor
168
17.9
18.2
17.4
mum chloride)]
Figure 8
Effect of Metal Ion Concentration on Ion Transport
Metal Ion Transport Rate, mm '
Low Concentration*
Membrane
E11Q4
E12Q4
E16Q1
EI8Q1
Cu
3.1
2.3
2.5
2.2
Cd
2.8
2.2
1.6
1.4
Zn
1.9
2.9
0.7
0.6
High Concentration**
Cu
1.5
0.7
0.6
1.41
Cd
1.5
0.8
0.9
0.6
Zn
1.5
0.6
+
0.4
* Nominal 50 ppm in metal ion.
** Nominal 500 ppm in metal
f Membrane ruptured.
ion.
Figure 9
Properties of High Transport Rate Membranes
Membrane
number
E11Q4
E12Q4
E16Q1
EI8Q1
Membrane
Type
(4-VP)CH,l
(4-VP/N-VP)CH,I
(VCB)(CH,)iN
(VBC/N-VPKCH,),H
Equilibrium
Water Content
g HiO/g
1.08
2.45
1.52
1.00
Ion-Exchange
Capacity
meqldry g
2.5
2.6
22
2.2
metal-cyanide complex anions was obtained. It can be seen
that the rate constants for metal removal are somewhat
lower for this anion-exchange membrane than those
observed for the cation-exchange membrane. This is
primarily due to the lower ion-exchange capacity of the
anion membrane (1.8 meq/g) compared to the capacity of
the cation membrane (2.3 meq/g).
Subsequent to this in-house research, a program was
conducted with the Industrial Environmental Research
Laboratory, Environmental Protection Agency, Cincinnati,
Ohio, for the development of improved membranes for
Donnan dialysis. The objective of this program was aimed at
developing anion-exchange membranes for the removal of
Figure 10
Replicate Evaluations of Membrane E11Q4
Metal Ion Transport Rate, mm
Low Concentration* High Concentration**
Membranes^
EIIQ4J
E1IQ4-B
EHQ4-C
* Nominal 50 ppm in metal ion
"Nominal 500 ppm in metal ion.
+Separate sets of membranes— same
I from Figure 8.
Cu
3. 1
3.4
3.2
'rafting run,
Cd Zn Cu
2.8 1. 9 1. 5
3 I 2.0 1.5
2.7 2.1 1.6
separate quatermzation reaction
Cd Zn
I.5 1.5
1. 3 1. 3
I 4 1.3
93
-------
metal-cyanide complex anions from electroplating process
washwaters.
The emphasis was placed on anion membranes due to two
reasons. First, there are available cationic membranes
developed for other purposes (electrodialysis, chlorine-
caustic electrololytic membrane cells) which have the
requisite mechanical and chemical properties to provide
good performance in Donnan dialysis for cation removal.
Eisenman (4) has reported on both laboratory and field
evaluation of Donnan dialysis for the recovery of nickel
from the rinse water on a Watts-type nickel plating line. This
work utilized modular tube and shell-type dialyzers with
each module containing about 380 tubes (0.025 in ID) to
provide 20 ft2 of membrane area. The dialysis system,
containing six modules with a total of 120 ft membrane
area, was capable of nickel removal rates of 2 g/hr/ft2 when
operated with 1 to 1 normal acid strip.
Secondly, the available anion-exchange membranes have
lower ion-exchange properties and are prone to fouling,
making them less useful for Donnan dialysis.
During this program, membranes were prepared by
grafting polyethylene basestock (1 mil thickness) with either
2-vinylpyridine, 4-vinylpyridine, or vinylbenzyl chloride.
After grafting, the membranes were quaternized. The
vinylpyridine-grafted films were quaternized with alkyl
halides; the vinylbenzyl chloride-grafted films were
quaternized with trialkyl amines. The degree of grafting (and
ultimately the ion-exchange capacity) was varied by using
different concentrations of monomer in the grafting
reaction. The hydrophilicity of the membranes was varied
by use of different alkylating reagents.
The membrane test system was modified to increase the
membrane area and to operate with single pass feed solution
and stripping solution recirculation. All preliminary
membrane evaluations were conducted with feed consisting
of electroplating bath solutions diluted to give metal ion
concentrations of nominal 50 ppm. All membranes were
evaluated using feeds containing copper, cadmium, or zinc
as their cyanide complex anions. The initial evaluation
indicated that the ion transport rates across the membrane
are proportional to the ion-exchange capacity, i.e., the
higher the ion-exchange capacity, the higher the transport
rate. It was also found that membrane hydrophilicity plays
an important role in ion transport. Membranes of low
hydrophilicity which imbided only small amounts of water
had low to zero ion transport rates regardless of ion-
exchange capacity. Ion transport rates increased with
increasing hydrophilicity up to a point and then decreased. If
a membrane absorbs large volumes of water, the charge
density within the membrane is decreased due to the large
wet volume of the membrane, and there is a loss of ion
selectivity. The decreased fixed charge density leads to less
rejection of cations; cation leakage across the membrane
leads to decreased Donnan potential across the membrane
and results in reduced ion transport rates.
Four membranes were selected for more extensive
evaluation. Two membranes were based on 4-vinylpyridine
and two on vinylbenzyl chloride-grafted films. These
membranes were evaluated at metal feed concentrations of
nominal 50 ppm and nominal 500 ppm for all three metals of
interest. The results are shown in Figure 8. All tou
membranes showed reasonable transport rates at 50 ppn
feed. There is a reduction in rate for all membranes on goinj
to 500 ppm feed. This is primarily due to change in the feec
concentration to stripping solution concentration ratk
which led to a lower driving force for ion transport. To havt
maintained the same ratio with the 500 ppm feed as was usec
with the 50 ppm feed would have required 2.0 normal NaC
stripping solution. For these anion-exchange membranes
that concentration of stripping solution would lead tc
excessive chloride ion leakage and very low transport rales
The two membranes E12Q4 and E16Q1, which showed the
poorest performance at the high level feed, are the more
hydrophilic of the four, as shown in Figure 9. Membrane
E11Q4 showed the best overall performance, indicating the
best balance of ion-exchange capacity and hydrophilicity.
Replicate studies of membrane El 1Q4 were conducted
using three different sets of membranes. The membranes
were prepared using material from the same grafting run but
which were quaternized in separate batches. Metal ion
transport rates for all three sets of membranes for all three
metals at both low and high metal ion concentrations were
made, with the results shown in Figure 10. These results
showed that uniform grafting and quaternization can be
obtained in the membrane preparation, as indicated by the
uniformity of the rate constants obtained.
Based upon these results, a field evaluation of a prototype
Donnan dialyzer is currently in the planning stages. These
plans call for preparation of sufficient quantities of
membrane El 1Q4 (400 to 800 ft2) to construct a prototype
plate and frame dialyzer. Calculations based upon the above
data indicate that this unit should give > 95% removal of
electroplating washwaters containing nominal 500 ppm
levels of copper, cadmium, or zinc at feed flow rates of 3 to 5
gpm.
This dialyzer will be operated on washwaters in
commercial electroplating shops to provide engineering data
on membrane performance and on long-term stability of the
membranes under actual use conditions. The field data
obtained should also allow assessment of the cost
effectiveness of Donnan dialysis as a means of controlling
effluent emissions levels in electroplating process wastewater
discharges.
References
\. F. G. Donnan, The Theory of Membrane Equilibria,
Chem. Rev., 1 (1925) 73.
2. R. M. Wallace, Concentration and Separation of Ions
by Donnan Membrane Equilibrium, Ind. Eng. Chem.
Process Design Develop., 6 (1967), 423.
3. H. F. Hamil, unpublished data.
4. J. L. Eisenman, Membrane Processes for Metal
Recovery from Electroplating Rinse Water, presented at
the EPA/AES conference, Orlando, Florida, February
5-7, 1979.
This paper has been reviewed in accordance with the U.S.
Environmental Protection Agency's peer and
administrative review policies and approved for presenta-
tion and publication.
94
*US GOVERNMENT PRINTING OFFICE 1983-6 59-095/0561
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