&EPA
United States
Environmental Protection
Agency
Technology Transfer
EPA/625/4-87/018
Seminar Publication
Meeting Hazardous
Waste Requirements for
Metal Finishers
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TECHNOLOGY TRANSFER .EPA/625/4-87/018 Sept. 1987
Seminar Publication
Meeting Hazardous
Waste Requirements for
Metal Finishers
September 1987
This document was published by:
U.S. Environmental Protection Agency
Center for Environmental Research Information
Office of Research and Development
Cincinnati, OH 45968
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This seminar publication is wholly based on edited versions of
presentations made at U.S. Environmental Protection Agency
(EPA) Technology Transfer Seminars on Meeting Hazardous
Waste Requirements for Metal Finishers. These seminars were
held in Boston, Massachusetts (September 10-11,1986);
Rosemont, Illinois (October 14-15,1986); and Los Angeles,
California (November 13-14,1986).
The following listing indicates the authors whose presenta-
tions are summarized in this publication.
» Chapter One (An Overview of RCRA Regulations)
— Robert Axelrad, EPA Office of Solid Waste,
Washington, DC.
• Chapter Two (Delisting Procedures) — Kenneth Schuster,
EPA Office of Solid Waste, Washington, DC.
" ChapterThree (Land Disposal Bans and Procedures for Ex-
tensions) —Gwen Porus, EPA Waste Management Divi-
sion, Boston, MA and Stephen Weil, EPA Office of Solid
Waste, Washington, DC.
* Chapter Four (Used Oil and Hazardous Wastes as Fuel) —
Michael Feeley, EPA Waste Management
Division, San Francisco, CA and John Podgurski,
EPA Waste Management Division, Boston, MA.
" Chapter Five (Underground Storage Tank and
Hazardous Waste Requirements — Jerry Phillips, EPA
Waste Management Division, Chicago, IL and Joshua
Workman, Los Angeles Municipal Sanitation District, Los
Angeles, CA.
» Chapter Six (Clean Water Act Update) — Jerry
Potamis, EPA Water Division, Boston, MA and Jerry
Phillips, EPA Waste Management Division, Chicago, IL.
» Chapter Seven (Detecting a Responsible Transporter and
Waste Management Facility), Albert C. Gray, JACA Corpo-
ration, Fort Washington, PA.
» Chapter Eight (The Costs and Benefits of Source
Reduction) —James Thibault, Environmental Control Sys-
tems, Providence, Rl.
" Chapter Nine (Materials Reuse and Recovery) — Marv
Drabkin, Versar Associates, Springfield, VA and Clarence
Roy, Rainbow Research, Stuart, FL.
» Chapter Ten (Organic Liquids: Treatment and Residues
Management) — Roberts. Capaccio, Mabbett, Capaccio &
Associates, Cambridge, MA.
• Chapter Eleven (Characterization and Treatment of Aque-
ous Wastes) — Mark Herein, Radian Corp., McLean, VA.
Orville Macomber (EPA Center for Environmental Research In-
formation, Cincinnati, OH) provided substantive guidance and
review for this document. Editorial and review assistance were
provided by Jenny Utz, Science Applications International Cor-
poration, McLean, VA; Clarence Roy, Rainbow Research, Stu-
art, FL; Louise Wise, EPA Office of Solid Waste and Emergency
Response, Washington, DC; Marv Rubin, EPA Office of Water
Regulations and Standards; and Chuck Marshall and Sheree
Romanoff, JACA Corp., Fort Washington, PA. Their contribu-
tions are gratefully acknowledged.
This report has been reviewed by the U.S. Environmental Pro-
tection Agency and approved for publication. The process al-
ternatives, trade names, and commercial products are only ex-
amples and are not endorsed or recommended by EPA. Other
alternatives may exist and may be developed. In addition, the
information in this document does not necessarily reflect the
policy of the EPA, and no official endorsement should be in-
ferred.
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Contents
Preface
1. An Overview of RCRA Regulations
Background 1
Federal Categories of Generators 1
Identifying Hazardous Waste 1
Counting Hazardous Waste 3
Storage and Transportation Requirements 3
Emergency Response Requirement 4
Reporting Requirements 4
2. Delisting Procedures
Introduction 6
Required Information and Analyses 6
Petition Review Process 7
3. Land Disposal Bans and Procedures for Extensions
Background 8
Proposed Rules and Regulatory Schedule 8
Who Is Affected 9
Summary 12
4. Used Oil arid Hazardous Wastes as Fuel
Background 13
Tracking Requirements 13
Hazardous Waste Fuel Defined 13
5. Underground Storage Tank and Hazardous Waste
Requirements
Background 15
The RCRA Subtitle I UST Program 15
The RCRA Subtitle C UST Program 17
6. Clean Water Act Update
Penalties 18
Hazardous Waste and the CWA 18
CWA and Municipalities 18
Stormwater Regulations 18
7. Selecting a Responsible Transporter and Waste
Management Facility
Background 20
Licensing 20
Selection Criteria for Transporters 21
Selection Criteria for HWMFs 22
Special Considerations 22
Summary 23
8. The Costs and Benefits of Source Reduction in Metal
Finishing
Introduction 24
Chemical Substitution 24
Waste Segregation 25
Process Modifications to Reduce Drag-Out Loss 25
Wetting Agents 25
Longer Drain Times 25
Other Drag-out Reduction Techniques 26
Waste Reduction Costs and Benefits 27
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9. Materials Reuse and Recovery
What Is Reuse/Recycling? 29
Wastes Produced in Metal Finishing Operations 29
Incentives for Recycle/Reuse 29
Electrolytic Recovery 30
Evaporation 32
Ion Exchange 34
Reverse Osmosis 37
Carbon Adsorption 39
Crystallization 39
Conclusions 41
10. Organic Liquids: Treatment and Residues Management
Why Treat? 42
Regulatory Overview 42
Organic Liquid Waste Management Program 42
Metal Finishing Process Operations 43
Chemical Substitution 43
Process Modifications 43
Waste Management Concerns 44
Waste Management Options 44
Treatment Process Residuals 47
11. Characterization and Treatment of Aqueous Wastes
Regulatory History of RCRA 48
Waste Characterization 48
Waste Segregation 48
Neutralization 49
Cyanide Containing Wastes 49
Chromium Containing Wastes 50
Arsenic and Selenium Containing Wastes 50
Other Metals Wastes 52
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The metal finishing industry is one of many industries
subject to regulation under the Resource Conservation
and Recovery Act (RCRA) and the Hazardous and Solid
Waste Amendments (HSWA) of 1984. The metal finish-
ing industry has also been subject to extensive regula-
tion under the Clean Water Act (CWA). Compliance with
these regulations requires highly coordinated regula-
tory, scientific, and engineering analyses to minimize
costs.
EPA's Office of Solid Waste and Emergency Response
has an ongoing outreach program to disseminate infor-
mation to the community regulated by RCRA and
HSWA. Thus, the metal finishing industry was selected
under this program as the focus of a series of seminars
for the dissemination of regulatory and technology in-
formation to aid plant managers and engineers to
achieve compliance in the most cost-effective manner.
Three seminars were held in the fall of 1986 in Boston,
Chicago, and Los Angeles. Support for the seminars
came from the American Electroplaters and Surface Fin-
ishers Society, National Association of Metals Finishers,
and the Metal Finishing Suppliers Association. This pub-
lication contains edited versions of what was presented
at each of the three seminars.
Events occurring after the seminars, made some of the
regulatory information presented at those meetings ob-
solete. Wherever possible, information has been updat-
ed and revised to take into account recent changes in
regulations. For example, the chapter on using hazard-
ous wastes as fuels was updated to reflect regulations
proposed in the spring of 1987.
This seminar publication provides information on the
regulations affecting hazardous wastes discharged by
metal finishers. Chapters are included on topics such as
the impact of RCRA regulations on both small and large
generators, the "delisting" of a specific facility waste
from hazardous waste regulation, land disposal bans on
hazardous wastes, the use of used oil and hazardous
wastes as fuel, criteria for the use of underground stor-
age tanks for hazardous wastes, the relevance of the
Clean Water Act to the hazardous wastes discharged by
metal finishers, the selection of a responsible hazardous
waste transporter and management facility, the costs
and benefits of source reductions in metal finishing,
materials reuse and recovery, the treatment and man-
agement of organic liquids, and the characterization and
treatment of aqueous wastes.
This publication is not a design manual, nor does it
include all the latest knowledge about metal finishing;
additional sources should be consulted for more de-
tailed information and design criteria. In addition, state
and local authorities should be contacted for regulations
applicable in local areas.
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1. An Overview of RCRA Regulations
Background
In 1976 Congress passed the Resource Conservation Re-
covery Act (RCRA) to address years of inattention to the
problem of hazardous waste disposal. In response, EPA
promulgated a body of hazardous waste regulations in
1980 including standards for generators of hazardous
waste, for those who transport hazardous waste, and for
facilities that treat, store, or dispose of hazardous waste. It
was at this time that EPA first defined "small quan-
tity generator" as a facility which generates less than
1,000 kg of hazardous waste per calendar month (roughly
2,200 pounds). These generators were basically exempted
from the regulations because of the impracticality of ad-
ministering a regulatory program for an estimated
500,000 businesses immediately. Instead, the regulatory
focus was directed at the larger generators that were esti-
mated to generate well over 90 percent of the country's to-
tal hazardous waste, and at permitting the existing treat-
ment, storage, and disposal (TSD) facilities. The small
quantity generator issue, including whether 1,000 kg was
or was not the most appropriate cut-off, was put on the
back burner.
Between 1980 and 1984 EPA began to look at the small
quantity generator issue, initiating a two-year study of the
types of wastes generated by small quantity generators
and how they are managed. As of November 1984,
though, no regulations had been proposed, and Congress
passed the Hazardous and Solid Waste Amendments, a
sweeping overhaul of the hazardous waste program that
required EPA to write some 93 different regulations and
reports. The use of deadlines known as "hammer provi-
sions" was also initiated to automatically impose require-
ments if EPA has not acted by specified dates. One ham-
mer provision was the requirement that EPA issue
regulations before March 31,1986 to lower the small
quantity generator cut-off from 1,000 kg to 100 kg per cal-
endar month.These regulations became effective Septem-
ber 22,1986.
By lowering the cut-off to 100 kg per month, companies in
virtually every manufacturing and service industry now
may be subject to regulation. By far the largest category is
vehicle maintenance facilities, including auto body and re-
pair shops, fleet maintenance facilities, and gas stations.
Other large groups are dry cleaners and industrial laun-
derers, firms that generate photographic waste, and the
metal working industries, including metal finishers.
A recent EPA study addressed the metal working industry,
including the types of waste generated and how regula-
tions would affect it. It is estimated there are as many as
11,000 metal manufacturing establishments operating in
the United States that may fall within the new small quan-
tity generator rules. Metal working operations include
forging, screw machine products, spring manufacturing,
metal stamping, fastener production, heat treating, and
electroplating. These processes generate a variety of
wastes considered hazardous, including cyanide, ignitable
paint, solvent still bottoms, spent solvents, spent plating,
strong acids and alkalis, and wastewater sludges contain-
ing heavy metals. These last four categories together re-
present more than 90 percent of metal working waste.
Federal Categories of Generators
In drafting the new regulations EPA was bound by two
very specific congressional mandates. One was to impose
requirements strict enough to protect human health and
the environment; the other was to minimize the burden of
regulations on small businesses. In regulating the large
quantity generator, the only consideration is the first man-
date. The second mandate has the effect of setting apart
the small quantity generator from other types of gener-
ators. Congress also established certain minimum re-
quirements that have been incorporated into the final
small quantity generator rules. Some of these require-
ments are designed to help small businesses, such as
longer storage periods to allow larger, and thus more eco-
nomical, shipments. Other requirements treat small busi-
nesses the same as large hazardous waste generators re-
quiring, for example, that waste be transported via a
hazardous waste transporter to a hazardous waste facility.
Table 1.1 lists the three Federal categories of generators.
First, there is the conditionally exempt small quantity
generator that generates less than 100 kg of hazardous
waste in a calendar month and less than 1 kg of certain
acutely hazardous waste (generally on the P list in EPA's
Part 261 List of Hazardous Wastes). The second category
is the small quantity generator, falling within the limits
of 100 kg to 1,000 kg per month (or about half of one 55-
gallon drum to about five 55-gallon drums of waste).
The third category is the large quantity generator that
generates more than 1,000 kg per month. There are sig-
nificant differences between the categories in the way
the wastes are managed, but all generators have two re-
quirements in common. First, they must determine if
their wastes are hazardous; second, they must deter-
mine how much waste they generate.
Identifying Hazardous Waste
In general, waste material comes into the Federal haz-
ardous waste regulatory system in one of two ways.
First, the waste or waste components may be specifical-
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RCRA REGULATIONS
Table 1.1. Steps to Comply with Federal Regulations for Hazardous Waste Generators
Conditionally Exempt
Small Quantity Generators
(producing no more than
100 kg/mo or less than 1
kg of acute HW)
Small Quantity Generators
of 100 -1,000 kg/mo
(and conditionally exempt
generators that accumulate
more than 1,000 kg on-site)
Large Quantity Generators
of more than 1,000 kg/mo
(or that generate or
accumulate more than 1 kg
of acute HW at any time)
Determine if you generate hazardous
waste.
"Count" your hazardous waste.
Send your waste to a facility that is at
least approved by a state to manage
municipal or industrial solid waste.
Avoid accumulating more than 1,000 kg
on-site at any one time.
Determine if you generate hazardous
waste.
"Count" your hazardous waste.
"Notify" EPA of hazardous waste activ-
ity and obtain a US EPA ID number.
Accumulate waste on-site in tanks or
containers for no more than 180 days or
270 days if waste must be shipped more
than 200 miles. (Other forms of on-site
storage require a permit.)
Comply with container standards or
special SQG tank standards when accu-
mulating waste on-site.
Be prepared to respond to emergencies
by designating an emergency coordina-
tor and post emergency numbers by the
phone. Ensure that employees under-
stand waste management and emer-
gency procedures. Report serious spills
or fires to the National Response Cen-
ter.
Your waste may only be disposed of at
a facility that has obtained RCRA inter-
im status or an RCRA hazardous waste
permit.
When shipping hazardous waste off
your premises:
• Use only transporters with EPA ID
numbers.
• Comply with DOT requirements for
packaging, labeling, and marking.
• Use the full Uniform Hazardous
Waste Manifest.
» Ship waste only to hazardous waste
facilities approved for your waste
type.
• Keep records for 3 years of manifests
which are returned by the designated
facility.
• Report missing shipments. Obtain an
RCRA permit if you store wastes in
other than tanks or containers, dis-
pose of hazardous waste at your site,
or conduct certain kinds of treatment.
Determine if you generate hazardous
waste.
"Count" your hazardous waste.
"Notify" EPA of hazardous waste ac-
tivity and obtain a US EPA ID num-
ber.
Accumulate waste on^site for no more
than 90 days in tanks and containers.
(Other forms of on-site storage require
a permit.)
Comply with container standards and
new tank rules.
Prepare and retain a written contingen-
cy plan for dealing with emergencies.
Prepare a personnel training plan. Re-
port serious spills or fires to the Nation-
al Response Center.
Your waste may only be disposed of at
a facility that has obtained RCRA inter-
im status or an RCRA hazardous waste
permit.
When shipping hazardous waste off
your premises:
• Use only transporters with EPA ID
numbers.
• Comply with DOT packaging, label-
ing, and requirements for marking.
• Use the full Uniform Hazardous
Waste Manifest.
• Ship waste only to hazardous waste
facilities approved for your waste
type.
• Keep records for 3 years of manifests
which are returned by the designated
facility.
• File an exception report with the state
or EPA Regional Office.
Submit a biennial report of your hazard-
ous waste activities during odd-num-
bered years. Include waste minimiza-
tion information.
Obtain an RCRA permit if you store
wastes in other than tanks or contain-
ers, dispose of hazardous waste at your
site, or conduct certain kinds of treat-
ment.
Check with your state hazardous waste management agency
to determine exactly what rules (including state requirements) apply to you.
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RCRA REGULATIONS
ly listed as hazardous on EPA's list. There are about 400
materials on the list, including several metal finishing
wastes, for example, listed with'designated waste ID
numbers F06 through F012. The second way a material
comes into the hazardous waste regulatory system is by
exhibiting at least one of the four following characteris-
tics based on testing or knowledge of its properties. An
ignitable hazardous waste is flammable or easily com-
bustible; for example, paint wastes and solvents. Waste
that corrodes metals or burns the skin is likely to be a
corrosive waste, such as the strong acids used in metal
forming processes. AreacfrVe hazardous waste is inher-
ently unstable and can undergo rapid or violent change
when it comes into contact with water; for example, the
strong oxidizing agents used in metal finishing. EP toxic
wastes have high concentrations of certain metals or
pesticides. To summarize, if it is not a listed hazardous
waste and it has not been mixed with a listed hazardous-
waste, and if it is not exhibiting one of the above charac-
teristics, it is not in the RCRA system (though it may be a
material that falls under state regulations). A very im-
portant aspect of the rules is this: As a generator, you
are responsible for determining whether you generate a
hazardous waste.
RCRA was designed to establish a minimum set of re-
quirements; but the states are free to establish regula-
tions that go beyond the Federal in stringency. There-
fore, generators must get specific state information in
order to know the requirements with which they must
comply.
Counting Hazardous Waste
There are four basic principles to counting,.or determin-
ing the quantity of waste generated. First, material still
in the production process is not counted until it is re-
moved from the process; for example, baths being con-
tinually used and reused, or a spent solvent still in the
production process or in the machine. Second, waste is
counted only once in a calendar month. In some cases,
for example, a waste may be used more than once a
month by recycling it on-site. It used to be that the waste
had to be counted every time it was recycled, so theo-
retically, while the initial quantity might be only five gal-
lons, legally a generator could be responsible for many
times that quantity over the course of a month. Under
the current rules only the initial quantity is counted.
Third, wastes discharged to a publicly owned treatment
works, if they are discharged directly and legally, in
compliance with the Clean Water Act Pretreatment Stan-
dards, are not covered under the RCRA system. Finally, a
general guideline for what is counted is any material
that is either a characteristic or a listed hazardous waste,
and that is accumulated after its removal from the pro-
cess before being sent off-site for treatment, storage, or
disposal. It is important to understand that this is not a
waste-stream-by-stream count, but one combined total
of all of the hazardous wastes generated at any individ-
ual site, with a site defined as a contiguous geographic
property. This is the quantity that determines the cate-
gory a generator falls under.
A facility meeting the test for a conditionally exempt
generator, that is, generating less than 100 kg per month
and less than 1 kg of acute hazardous waste, is out of the
system provided the waste is sent to a facility that is at
least state-approved. That is not necessarily a hazardous
waste facility, although the state may insist that it be a
hazardous waste facility. It might be a recycling facility
or a solid waste facility; but under Federal rules the
waste does not have to go to a hazardous waste facility if
there is under 100 kg per month total. A conditionally
exempt generator that accumulates more than 1,000 kg
on-site at any time becomes subject to the small quanti-
ty generator standards.
Small quantity and large quantity generators are in the
system and must have identification numbers for their
facilities. An ID number is obtained by filing a form
called Notification of Hazardous Waste Activity, avail-
able either through the state or the EPA regional office.
This form only has to be filed once.
Facilities with no regular pattern of waste generation,
called episodic generators, may move from one cate-
gory to another in any given month. Though legally they
are subject to the more stringent requirements only in
the month or months they fall into the higher categories,
as a practical matter they will probably want to always
be in compliance with the most stringent requirements
to minimize paperwork and procedures.
Storage and Transportation Requirements
The allowable storage periods differ between the large
quantity generator and the small quantity generator. A
large quantity generator gets 90 days to store waste pn-
site without a permit. In order to accumulate economical
shipments, a small quantity generator gets 180 days to
accumulate waste on site and an additional 90 days if
the waste is shipped farther than 200 miles from the
generator's site. The facility is allowed to accumulate up
to 6,000 kg of hazardous waste on-site without getting
an RCRA permit. When waste is accumulated on-site cer-
tain standards must be complied with. Accumulated
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RCRA REGULATIONS
wastes must be stored in tanks or containers only; stor-
ing accumulated waste in a surface impoundment or
pond, for example, is not a generator activity, it is a per-
mit and storage activity requiring a special permit.
The container and tank standards are different for the
small quantity generator than for the large quantity gen-
erator, largely in regard to paperwork; differences are
not substantive except in two cases. First, large quantity
generators storing ignitable and reactive wastes in con-
tainers are subject to a 50 foot buffer zone requirement
— in other words, that material must be stored at least
50 feet from the property line. Small quantity generators
are exempt from that requirement, but they must store
the material as far from the property line as practical.
Second, tank rules have recently been modified for large
quantity generators and now require secondary contain-
ment for new tanks as well as for leaking tanks or tanks
15 years old or older. The small quantity generator is not
subject to the secondary containment rules. The con-
tainer standards which apply to the small quantity gen-
erator say only that the container must not leak, and if it
does leak, the material must be transferred to nonleak
fng containers.
Shipping waste off-site is costly and subject to a consid-
erable number of requirements. First, the transporter
must have a U.S. EPA ID number whether the waste
comes from a small or large quantity generator. The
states have the option of modifying the uniform mani-
fest, so the forms may differ from state to state. Conse-
quently, a generator is required to use the manifest of
the destination facility's state. Both large and small gen-
erators must also comply with DOT requirements for
packaging, labeling, and marking containers. Gener-
ators should be able to get help from the transporter, !
though the generator must sign the manifest and cannot
delegate liability.
Both categories of generators must complete a full uni-
form hazardous waste manifest which basically requires
identification of the transporter and the facility to which
the waste is being delivered. Other information is re-
quired that could be used by the transporter in case of a
problem, including the type of waste and its hazard char-
acteristics. This also provides the RCRA tracking mecha-
nism for identifying who had the waste last if the waste
does not get to its designated site. There is an exception
reporting requirement whereby a large quantity gener-
ator is required to notify EPA or the state office if no writ-
ten confirmation of the shipment is received. The gener-
ator must keep these receipts, which are signed copies
of the manifests, for three years from the date of the last
shipment. The small quantity generator had been re-
lieved of this exception reporting requirement, but
recently EPA adopted a simplified exception reporting
system for small quantity generators. Under this sys-
tem, the generator (in lieu of a formal report) may sub-
mit a photocopy of the original manifest along with a
handwritten note stating it was not returned by the
facility.
Emergency Response Requirement
Changes have also been made in the emergency re-
sponse regulations. Large quantity generators must
now have detailed written contingency plans in their
files at all times which explain in detail how they will re-
spond to emergencies and details of their personnel
training program. The small quantity generator must
post near the telephone a listing of the names of emer-
gency response officials, fire officials, the National Re-
sponse Center, the emergency coordinator, and other in-
formation, and, like a large quantity generator, must
designate someone to be called in the case of a fire or
spill or other problem at the facility who can get to the
facility within 20 minutes. No paper plan is required for
the small quantity generator. Similarly, where the large
quantity generator must have a formal personnel train-
ing system in place, the small quantity generator only
has to ensure that his employees understand the waste
management and handling techniques that are impor-
tant to their jobs, but no paper plan is required.
Reporting Requirements
Two waste minimization requirements are now in place
under the Federal rules. Waste minimization is consid-
ered to be either source reduction or recycling. One re-
quirement is a two-part certification statement to the
uniform hazardous waste manifest. The first part certi-
fies the accuracy of the information the generator is pro-
viding on the form; the second part states that the gen-
erator has a program in place to minimize waste genera-
tion to the extent he has deemed economically
practicable and has selected the best waste manage-
ment method that is economical, available, and mini-
mizes potential harm to human health and the environ-
ment. For the small quantity generator this statement
takes the form of affirming a good faith effort to mini-
mize waste generation and select the best waste man-
agement method available and affordable to the gener-
ator. So that instead of stating that a program is in place,
as a large generator must, this certification simply states
that a good faith effort is being made.
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RCRA REGULATIONS
Finally, a large quantity generator must file a biennial re-
port detailing the kinds of activities he has conducted,
the types of waste he has generated, and where that
waste was sent. The biennial report must also contain a
narrative description of the generator's waste minimiza-
tion efforts.The small quantity generator has no biennial
report requirement.
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2. Delisting Procedures
Introduction
EPA lists hazardous wastes by category (e.g., all inorganic
sludges of a certain type), and by whether or not they pos-
sess any of the four characteristics of ignitability, toxicity,
corrosJvity, and leachability. Wastes designated as hazard-
ous because of one or more of the four characteristics
cannot be delisted. However, an individual industrial facili-
ty's listed waste(s) may not be hazardous despite entire
categories of waste having been designated as hazardous!
The regulations (40 CFR 260.20 and 260.22) therefore al-
low for a petition mechanism to delist a specific facility
waste from hazardous waste regulation. Delisted wastes
from that facility only, can be disposed of in regular solid
waste facilities, or otherwise managed as a solid waste. A
guidance manual (Petitions To Delist Hazardous Wastes -
A Guidance Manual, NTIS No. PB85-194488) has been is-
sued to detail the delisting procedures for wastes which
do not meet any of the listing criteria, do not exhibit any of
the hazardous waste characteristics, or do not contain oth-
er toxicants at hazardous levels.
Under Subpart B of Part 261, EPA lists wastes as hazard-
ous if they exhibit the characteristics of ignitability, corro-
sivlty, leachability, or toxicity, are acutely hazardous (fatal
to humans in low doses or meet certain oral, inhalation,
and dermal LDgo levels for lab animals), or contain one or
more of 350 listed hazardous constituents. There are three
categories of hazardous wastes: those from non-specific
sources, those from specific sources, and specific com-
mercial chemical products. :
Required Information and Analyses
The delisting procedures as revised per the Hazardous
and Solid Waste Amendments (HSWA), Section 222, re-
quire that the EPA consider factors (including additional
constituents) other than those for which the waste was
listed, as well as the original listing criteria. Information re-
quired includes: all raw materials, intermediates, and final
products categorized as process materials, discharged
process materials, or nondischarged process materials;
analytical data or a mass balance demonstration for all
hazardous constituents expected to be present in signifi-
cant levels and a rationale for those constituents not ex-
pected to be present at significant levels; and test results
for the hazardous waste characteristics of reactivity, igni-
tability, and corrosivity (or rationale in lieu of); total con-
stituent and leachate analysis; and total oil and grease.
A full year's ground water monitoring data is also required:
for petitions requiring exclusion of on-site waste disposal
units.The ground water monitoring data should include
location of monitoring wells, direction of ground water
flow, hydrogeological characteristics of the site, and sam-
pling and analysis procedures. In addition, general admin-
istrative information, process information (with schemat-
ics), waste stream information (including hazardous waste
numbers, generation rates, etc.), and sampling and testing
information (including laboratory details; test dates, meth-
ods, and equipment; and QA/QC provisions) are required.
Also the Oily Waste EP leachate test must be used when
the oil and grease content of the petitioned waste exceeds
one percent.
There are three major parts to the delisting process.
Submitting the petition should be preceded by prelimi- •
nary consideration of why the waste was listed as haz-
ardous, to whom the petition should be addressed, and
the content of the petition. The first section of the peti-
tion will contain administrative information relative to
the individual or firm, the specific waste-generating fa-
cility, the company personnel, and the requested delist-
ing action. The production processes section of the peti-
tion requests information on the manufacturing
operation or other processes which generate waste. Suf-
ficient information must be submitted to determine
what hazardous waste characteristics and toxic constitu-
ents might be present. The petition may contain either a
list of raw materials or test results for hazardous con-
stituents.
Examples of general process information for operations
which produce a listed waste would include descriptions
of production lines and equipment including typical
stages in the operating cycle(s), description of surface
preparation, cleaning, or coating operations, and sup-
portive schematic diagrams for the above. In assessing
the hazard of the wastes, two approaches are available.
Generally, Approach A requires test results for hazard-
ous constituents; hazardous waste characteristics; lea-
chate concentration of the (EP) toxic metals, nickel, and
cyanide; total concentrations and a mass balance dem-
onstration of the EP toxic metals, nickel, and cyanide;
and total oil and grease. A complete list of raw materials,
intermediates and end products is required (categor-
izing each as either discharged into the waste stream or
not discharged into the waste stream). Under this first
approach, an assessment is required of the likelihood of
new waste streams being produced.
Approach B involves the same test results on four repre-
sentative samples called for in approach A (hazardous
waste characteristics; leachate and total tests for EP tox-
ic metals, nickel, and cyanide; Appendix III testing and
total organic carbon; and total oil and and grease). In-
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DELISTING PROCEDURES
stead of supplying lists of raw materials, intermediates,
and end products, the petitioner is required to supply ex-
planations for the hazardous constituents not expected
to be found.
The waste stream section of the petition calls for a de-
tailed description of the waste stream to be delisted. The
specific information used to describe the stream in-
cludes EPA hazardous waste numbers, common name,
and physical form for each waste. The petitioner is re-
quested to submit average and maximum monthly and
annual generation rates as per the operating records,
and to describe whether the petitioned wastes are cur-
rently being generated, planned to be generated, or are
no longer generated. A description of past and current
waste management methods is also required along with
appropriate schematics, as are names and locations of
off-site treatment, storage, or disposal facilities.
An engineering analysis of a waste stream can usually
result in the reduction of the list of hazardous constitu-
ents that must be included in the demonstration, by em-
ploying mass balance techniques and examining likely
chemical reactions. Mass balance for a process will
show raw materials input, use rates, and likelihood of
their presence in the waste stream. Expert chemical
judgment must sometimes be applied to predict the by-
products of the reactions. Generally, the more detail pro-
vided in the engineering analysis the greater the likeli-
hood that the petitioner's mass balance demonstration
will be accepted. Mass balance techniques may not be
possible for nonprocess applications.
Petition Review Process
The petition review process by EPA first involves ah ini-
tial review to determine the completeness of the peti-
tion. Once the petition is judged to be complete a tenta-
tive decision is made to grant or deny. (Denial decisions
are often made before a petition is complete, if adequate
information is available.) If a decision is made to deny
the petition, the petitioner is sent a letter that explains
the reasons for the denial decision and presents the op-
tion to withdraw the petition. Otherwise, all proposed
Agency decisions are printed in the Federal Register.
A workgroup of EPA Office of Solid Waste (OSW) mem-
bers and other staff members evaluates the draft pro-
posed notices, submits comments to OSW, and follow-
ing review of all comments, sends the proposed notice
to the Office of General Counsel for comments. The pro-
posed recommendation is sent to the Assistant
Administrator for Solid Waste and Emergency Response
who decides whether to approve the Office's decision.
The decision of the Assistant Administrator is published
in the Federal Register with a request for comments
within 30 days. Following the comment period and re-
view of the comments, the decision is reviewed by the
workgroup and the above process repeated. The Assis-
tant Administrator's final decision is then published in
the Federal Register as a final rule.
Of the 698 total petitions received to date, 30 percent
were withdrawn, 9 percent passed, 14 percent were de-
nied, 26 percent were "mooted" (i.e., not a hazardous
waste by definition), 3 percent were referred to state de-
listing programs (before HSWA removed authority), and
18 percent are still actively under review.
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3. Land Disposal Bans and Procedures for
Extensions
Background
When the RCRA Amendments came into effect on Novem-
ber 8,1984, the scope of RCRA regulations was greatly ex-
panded; many of these new provisions involved restrict-
ing wastes from land disposal. The first of these became
effective six months after enactment, in May 1985, and
banned bulk and noncontainerized hazardous liquids from
disposal in landfills. In November 1985, a year after enact-
ment, nonhazardous liquids were banned from disposal in
landfills.These two bans remain in effect in addition to the
new waste-by-waste restrictions outlined in this discus-
sion.
These new provisions have broadened the definition of
land disposal to include placement of hazardous wastes in
landfills, surface impoundments, waste piles, injection
wells, land treatment facilities, salt domes or salt forma-
tions, and underground mines or caves. It is estimated
that about 33 billion gallons of untreated hazardous waste
now go to these land disposal units, and current thinking
is that even properly engineered units with liners and leak
detection systems may not be enough to prevent the re-
lease of hazardous constituents from these units to
ground water, surface water, or air.
National concern has culminated in this congressional
mandate that reliance on land disposal must be mini-
mized or eliminated, and that land disposal should be the
least favored method for managing hazardous wastes.
Ths expectation is that these land disposal restrictions will
eventually lead to an overall reduction in waste genera-
tion, and an impetus to recycle rather than just dispose.
Treatment of organic wastes is expected to be through
such methods as incineration or neutralization, and inor-
ganics through stabilization or fixation techniques. While it
is recognized that there will always be some residuals that
will have to be land disposed, it is expected this will occur
after treatment and that the volume of wastes to be land
disposed will be greatly reduced.
Proposed Rules and Regulatory Schedule
The proposed rules discussed here were published in
the Federal Register, January 14,1986. Under the 1984
Amendments to RCRA, land disposal of hazardous
wastes is prohibited unless the waste has been treated
in accordance with standards set by EPA, or unless it can
be shown that continued land disposal of hazardous
wastes is protective. EPA has been charged with setting
treatment standards for approximately 450 hazardous
waste streams. These are the listed wastes and charac-
teristic wastes, identified in 40 CFR 261. HSWA prohibits
the wastes from land disposal unless treated to stan-
dards set by EPA in a phased approach between Novem-
ber 8,1986 (solvents and dioxin containing wastes) and
May 8,1990. The treatment standards may be set as per-
formance standards, allowable concentrations of haz-
ardous constituents in a waste extract or in the waste, or
as specified technologies. Wastes containing higher lev-
els than the specified treatment standards or not treated
by the specified technology, can only be land disposed
after these dates by successfully demonstrating that
there will be no migration of these constituents from the
land disposal unit for as long as the waste remains haz-
ardous.
In promulgating these treatment standards for each
waste stream, EPA will in effect determine what can
safely be land disposed and at what levels. The obvious
objective is to minimize threats to ground water or sur-
face water through leaching and to the air through emis-
sions. This will generally be accomplished by reducing
the toxicity and mobility of the wastes before they are
land disposed. First, EPA will have to identify and evalu-
ate appropriate treatment technologies in terms of their
applicability to specific waste streams, how widespread
their uses are, and their overall effectiveness in reducing
the toxicity and mobility of wastes.
Treatment standards will be set out in Part 268 of 40CFR.
They will be expressed as constituent concentrations in
a waste or waste extract or as specified technologies,
and land disposal will be allowed when the relevant
standards have been met. If the concentration of any of
the hazardous constituents in a waste or waste extract
as applicable, equals or exceeds the level indicated in
the regulations, then the waste must be treated before
being land disposed. If concentrations are below these
levels, then the waste may be land disposed through
normal channels without treatment. In addition, specific
technologies that have been shown to be effective in re-
ducing toxicity in certain waste streams will be identi-
fied in the preamble to the regulations. However, any
method may be used to treat wastes exhibiting concen-
trations over the allowable limits, except where specific
technologies are required.
Congress set up a four-year schedule which started No-
vember 8, 1986. This was the first deadline for the first
group of wastes to be prohibited—solvents and dioxins,
and EPA published its regulations on November?, 1986.
EPA also set out a schedule for ranking and restricting
the remaining listed waste streams, putting high volume
wastes and high hazard wastes at the top of the list for
the earliest bans. This schedule was published on May
28,1986 (51 Federal Register 19300). On the second
date, July 8,1987, the final prohibition for the "Califor-
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LAND DISPOSAL BANS
nia List of Wastes" will be published in the Federal
Register. The California List is so called because the
State of California deemed that these wastes should be
banned from land disposal based on their toxicity, mo-
bility, and effects on liners in land disposal facilities.
These waste streams include wastes containing cya-
nide, several metals, acid wastes, PCBs, and halogenat-
ed organics.
The last group of wastes will be those that EPA has
ranked and divided into three categories. By August 8,
1988 the first third of these ranked listed wastes will be
prohibited. By June 8,1989 the second third of these
listed wastes will be prohibited, and by May 8,1990 the
last third of these listed wastes and all characteristic
wastes must be banned. If EPA misses these deadlines
and fails to set treatment standards for these different
groups of Wastes, then on the respective dates for sol-
vents, dioxins, the California List, characteristic wastes,
and the last third of the listed wastes, land disposal
will be banned. There is an "out" for the first and
second thirds of the listed wastes; they can continue to
be disposed of until 1990 in units meeting the minimum
technological requirements of HSWA (double liners, lea-
chate collection, ground water monitoring).
Who is Affected
How would generators actually go about determining
whether or not they are subject to these restrictions? Ta-
ble 3.1 goes through the steps for such a determination.
First, the generator determines from Part 268 of the reg-
ulations if his waste is listed or characteristic hazardous
waste. If it is not, then land disposal in nonhazardous
waste landfills may be used. If it is a listed or characteris-
tic hazardous waste, the next step is to determine
whether any of the hazardous constituents listed in the
table in the regulations exceed or equal the allowable
concentrations where this is relevant. If the constituents
are below the limits shown, then land disposal may con-
tinue to be used. If the limits are equalled or exceeded,
then the generator is subject to the restrictions. If a spe-
cific treatment technology is listed for that waste
stream, it must be used to treat that waste until accept-
able limits are reached. If a treatment is not specified in
the regulations, then any appropriate method can be
used that will reduce the levels to the allowable limits.
Those treated wastes can then be land disposed.
Exemptions or variances may be granted in certain cir-
cumstances. For example, one case-by-case extension
Table 3.1. Land Disposal Restriction Procedures
Generator
RCRA TSD Facility Operating
Under Interim Status
RCRA TSD Facility Operating
Under a Permit
Procedure T. Analysis to Determine Constituent Concentrations in Waste or Waste Extraxt (40 CFR 268.6 and 268.40(b)).
The.generator must determine, through
either testing or knowledge of the
waste, whether his waste meets the
trewatment standards under 40 CFR
Part 268 Subpart D. If the hazardous
constituents in the waste do not exceed
the concentrations listed in Table
CCWE,1 the waste is not subject to fur-
ther restriction under 40 CFR Part 268
although the generator must designate
on the manifest a land disposal facility
which is authorized to dispose of the
waste (40 CFR 262.20).
If the hazardous constituents in the
waste extract or waste is subject to the
land disposal restrictions and the gen-
erator must pursue one or more of the
available options under 40 CFR Part 268
(case-by-case extension, petition, or
treatment).
The facility must either have documen-
tation of tests conducted by the genra-
tor or test the waste to determine that
such waste is in compliance with appli-
cable treatment standards. The waste
must be tested using the methods de-
scribed in SW-846 or equivalent meth-
ods approved by the Administrator (40
CFR 268.6). The facility must record the
result of this testing in its operating re-
cord (40 CFR 265.73).
If the hazardous constituents in the
waste extract or waste do not equal or
exceed the 40 CFR Part 268 Subpart D
treatment standards, the waste is not
subject to further restriction under 40
CFR Part 268, although sti|l a hazardous
waste, and may be land disposed at an
RCRA facility which has authority to
manage the waste.
The facility must either have documen-
tation of tests conducted by the gener-
ator or test the waste to determine that
such waste is in compliance with appli-
cable treatment standards. The waste
must be tested using the methods de-
scribed in SW-846 or equivalent meth-
od approved by the Administrator (40
CFR268.6). The facility must record the
result of this testing in its operating re-
cord (40 CFR 264.73).
If the hazardous constituents in the
waste extract or waste do not equal or
exceed the 40 CFR Part 268 Subpart D
treatment standards, the waste is not
subject to further restriction under 40
CFR Part 268, although still a hazardous
waste, and may be land disposed at an
RCRA facility which has authority to
manage the waste.
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UNO DISPOSAL BANS
Table 3.1. continued
Generator
RCRA TSD Facility Operating
Under Interim Status
RCRA TSD Facility Operating
Under a Permit
Procedure 2a. Use of an Identified Technology to Treat a Restricted Waste (40 CFFt 268.40(a)>.
The generator must send its waste to a
facility that has the ability to treat the re-
stricted waste using the identified tech-
nology found under 40 CFR 268.41.
The treatment facility must be able to
apply the identified technology desig-
nated for the restricted waste comply-
ing with any standards specified for that
technology.
The treatment facility must provide cer-
tification of proper treatment to the land
disposal facility receiving the treatment
residue.
The treatment residue, after treatment
by the required technology(ies), must
be managed as a hazardous waste2 but
may be land disposed.
The treatment facility must be able to
apply the identified technology desig-
nated for the restricted waste comply-
ing with any standards specified for that
technology.
The treatment facility must provide cer-
tification of proper treatment to the land
disposal facility receiving the treatment
residue.
The treatment residue, after treatment
by the required technology(ies), must
be managed as a hazardous waste2 but
may be land disposed.
Procedure 2d. Use of an Equivalent Treatment Method to Treat a Restricted Waste (40 CFR 268.40(a)).
Th0 generator must send its waste to a
facility that has the ability to treat the re-
stricted waste using an Equivalent
Treatment Method approved by the Ad-
ministrator.
The treatment facility must petition the
Administrator for approvalof an Equiv-
alent Treatment Method in accordance
with 40 CFR 268.41 (b).
The treatment facility must provide cer-
tification of proper treatment to the land
disposal facility receiving the treatment
residue.
The treatment residue, after treatment
by the required technology(ies), must
be managed as a hazardous waste2 but
may be land disposed.
The treatment facility must petition the
Administrator for approval of an Equiv-
alent Treatment Method in accordance
with 40 CFR 268.41 (b).
The treatment facility must provide cer-
tification of proper treatment to the land
disposal facility receiving the treatment
residue.
The treatment residue, after treatment
by the required technology(ies), must
be managed as a hazardous waste2 but
may be land disposed.
Procedure 3. Case-by-Case Extensions of Effective Dates to Allow Continued Land Disposal of a Restricted Waste (40CF/? 268.4).
Generators seeking a case-by-case ex-
tension must apply to the Administra-
tor. The extension does not become ef-
fective until a notice of approval is
published In the Federal Register or the
generator receives an approval notice
from the Administrator. The generator
must forward a copy of the approval no-
tice to the land disposal facility receiv-
ing its waste before shipping the waste
to the facility. The generator must retain
the notice of approval in his records (40
CFR 262.40).
Land disposal facilities seeking a case-
by-case extension ;must apply to the Ad-
ministrator. The extension does not be-
come effective until a notice of approval
is published in the Federal Register or
the disposal facility receives an approv-
al notice from the Administrator. The fa-
cility must have a copy of the approval
notice in its operating record and must
keep an accounting of the waste dis-
posed under the extension (40 CFR
265.73(b)(8». This approval notice may
be forwarded by the generator or ob-
tained by the disposal facility directly.
Procedure 4. Petitions to Allow Land Disposal of a Restricted Waste (40 CFR 268.5).
The generator should have evidence The facility must submit a petition to
that the facility has an approved peti- the Director3 and receive a notice of ap-
tlon to land dispose of a specific re- proval before it can land dispose of a re-
stricted waste before shipping that wa- stricted waste. A copy of the approveal
sate to the facility for dispoal. The notice must be kept on file in the operat-
Land disposal facilities seeking a case-
by-case extension must apply to the Ad-
ministrator. The extension does not be-
come effective until a notice of approval
is published in the Federal Register or
the disposal facility receives an approv-
al notice from the Administrator. The fa-
cility must have a copy of the approval
notice in its operating record and must
keep an accounting of the waste dis-
posed under the extension (40 CFR
264.73(b)(10)>. This approval notice
may be forwarded by the generator or
obtained by the disposal facility direct-
ly.
The facility must submit a petition to
the Director3 and receive a notice of ap-
proval before it can land dispose of a re-
stricted waste. A copy of the approveal
notice must be kept on file in the operat-
10
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LAND DISPOSAL BANS
Table 3.1. continued
Generator
RCRA TSD Facility Operating
Under Interim Status
RCRA TSD Facility Operating
Under a Permit
generator, itself, may also file a petition
or be aparty to a petition with a treat-
ment, storage, and disposal facility.
ing record.
The facility must have interim status (or
an approved change under interim sta-
tus) to manage the restricted waste and
to operate the land disposal process.
The facility must comply with all condi-
tions of the approval.
ing record.
The facility must have have a permit
which includes (or must modify its per-
mit to include) the restricted waste
codes to be managed and the land dis-
posal process.
The facility must (through permit condi-
tions) comply with all conditions of the
approval.
Procedure 5. Treatment of Restricted Wastes in Certain Surface Impoundments (40 CFR 268.1 (ca)).
The generator must send its waste to a
treatment facility that has an impound-
ment that meets the minimum techno-
logical requirement, i.e., has been con-
structed with a double liner (with
limited exceptions) and is in compli-
ance with ground water monitoring re-
quirements.
Procedure 6. Land Disposal of Wastes that
The generator must determine, through
either testing or knowledge of his
waste, that his waste meets the 40 CFR
Part 268 Subpart D standards and is,
therefore, no longer a restricted waste,
before shipping the waste (with accom-
panying manifest) for land disposal ro a
facility with interim Status or an RCRA
permit.
The facility must have Interim Status (or
an approved change under Interim Sta-
tus) to manage the restricted waste and
operate the treatment process.
The impoundments must meet the
minimum technology requirements in
accordance with 40 CFR 265.221 (a)
through (e) and be in compliance with
40 CFR Part 265 Subpart F.
The facility must analyze the contents of
the impoundments annually in accor-
dance with 40 CFR 268.1 (e)(2).
Impoundment residue that does not
meet the standards found under 40 CFR
268.42 or 268.43 must be removed and
managed as a restricted waste, but can-
not be further treated in an impound-
ment.
Residue that meets the standards found
under 40 CFR 268 Subpart Dean remain
in the impoundment or can be other-
wise land disposed. The residue must
be managed as a hazardous waste.
Meet 40 CFR Part 268 Subpart D Standards
The facility must have Interim Status (or
an approved change under Interim Sta-
tus) to manage the waste.
The facility must have records and re-
sults of waste analysis performed (40
CFR 265.13 and 268.5), documenting in
the operating record that the waste
meets 40 CFR Part 268 Subpart D stan-
dards and may be land disposed with-
out further treatment.
The facility must have have a permit
which includes (or must modify its per-
mit to include) the restricted waste to be
managed and the treatment process to
be operated.
The impoundments must meet the
minimum technology requirements in
accordance with 40 CFR 264.221 (a)
through (e) and be in compliance with
40 CFR Part 264 Subpart F.
The facility must analyze the contents of
the impoundments annually in accor-
dance with 40 CFR 268.1 (e)(2).
Impoundment residue that does not
meet the standards found under 40 CFR
268.42 or 268.43 must be removed and
managed as a restricted waste, but can-
not be further treated in an impound-
ment.
Residue that meets the standards found
under 40 CFR 268 Subpart Dean remain
in the impoundment or can be other-
wise land disposed. The residue must
be managed as a hazardous waste.
The facility must have have a permit
which allows (or must modify its permit
to allow) management of the waste.
The facility must have records and re-
sults of waste analysis performed (40
CFR 265.13 and 268.6), documenting in
the operating record that the waste
meets 40 CFR Part 268 Subpart D stan-
dards and may be land disposed with-
out further treatment.
'Constituent Concentration in a Waste Extract, 40 CFR 268.41.
2Unless the residue has been delisted (40 CFR 260.22) or the residue is the result of treating a waste that is hazardous solely because it exhibits
one or more hazardous waste characteristics (40 CFR Part 261 Subpart C) and the residue no longer exhibits the characteristic(s).
3Director is as defined under 40 CFR 270.2.
11
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LAND DISPOSAL BANS
requires that the generator demonstrate that there is no
alternate capacity for his wastes; then an extension can
be granted for up to two one-year periods from the date
that waste would be banned. In order to get this exten-
sion the generator must show a binding contractual
commitment to provide or construct this alternate treat-
ment capacity by the end of the extension period. An-
other type of variance is an actual petition to continue
disposal of a particular waste in a particular unit. To do
that is much more complicated because the generator
must demonstrate that waste and site-specific factors
such as hydrogeology or other special considerations al-
low for degradation or immobilization of the waste so
that there is no migration of hazardous constituents
from the unit for as long as the waste remains hazard-
ous. This demonstration must also take into account any
receptors of the leachate or the constituents as they mi-
grate and show that they would not be affected at levels
that would endanger human health. When the final rul-
ing for the first group of wastes comes out for solvents
and dioxins, it is expected that a draft petitioner's guid-
ance manual will be issued.
Summary
The Federal Register notice dated July 8,1987 contains
the final ruling for the (California List) wastes covering
metals and cyanides. There is a 60-day comment period
allowed. Also, Headquarters has indicated that the stan-
dards coming out for the California Wastes will be those
listed in the actual statute; that is, the California Wastes
as they are defined. EPA may attempt to set lower limits
in a separate rulemaking. In any case, the limits in the
proposed rule will eventually end up being meaningless
because treatment standards will be set under another
category — the listed wastes.
12
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4. Used Oil and Hazardous Wastes as Fuel
Background
The November 29,1985 major rule pertaining to the use of
used oils and hazardous waste as fuels consisted of one fi-
nal set of interim regulations and two proposed regula-
tions, related to the HSWA amendments. The ruling
placed most of its emphasis on the marketers and
burners, and represented EPA's first attempt to regulate
the burning of used oil as fuel under RCRA. Interpretation
of the ruling is highly dependent on the understanding of
the definitions of the following concepts and terms: mar-
keter, burner, generator, waste fuel, hazardous waste fuel,
used oil fuel, used oil, characteristic waste, nonindustrial
burner, beneficial recycling, and on-spec/off-spec used oil
fuel. The term "waste fuel" encompasses both hazardous
waste fuel and used oil fuel. These definitions are distrib-
uted throughout the following text.
The major impact of the ruling is that the burning of haz-
ardous waste fuel or off-specification used oil fuel in non-
industrial boilers is prohibited. The specifications for used
oil fuel are arsenic (5 ppm), cadmium (2 ppm), etc. Used
oil fuels not meeting these specs are considered off-spec.
Only specification (on-spec) oil can be burned in nonin-
dustrial boilers.1 Any on- or off-spec used oil mixed with
listed hazardous wastes becomes a listed hazardous
waste and cannot be burned in nonindustrial burners. The
same holds true for used oil/characteristic hazardous mix-
tures that continue to exhibit a hazardous waste character-
istic. Nonindustrial boilers include residences and com-
mercial facilities such as laundries, hotels, office buildings,
and service stations. Notably, greenhouse boilers are clas-
sified as industrial boilers. The burning of these materials
can only be for energy recovery and not for destruction,
i.e., the material must have a heat value greater than ap-
proximately 5,000 Btu per pound. The burning of eligible
fuels is permitted only in industrial boilers, industrial fur-
naces, utility boilers, space heaters, and hazardous waste
incinerators. The two proposed regulations included list-
ing used oil as a hazardous waste and also hazardous
waste recycling standards.
The remaining concerns of the rules lie in the administra-
tive requirements which include notification, tracking, and
recordkeeping requirements. The notification require-
ments apply to all marketers of waste fuels, any generator
1The regulations do allow non-industrial boilers to burn hazardous
waste fuel and off-spec used oil if they are in compliance with the
hazardous waste incinerator (Subpart 0 of 40 CFR) requirements.
'In a November 17,1986 Federal Register notice, EPA published their
intent not to list used oil as a hazardous waste. Used oil remains
subject to the November 29,1985 management standards, however.
who ships waste fuels directly to a burner, and all burners
of hazardous waste fuels and off-spec used oil fuel. Mar-
keters and burners who have previously notified EPA and
have an ID number must renotify in order to complete an
expanded fuel information section.
The party that first claims that a used oil fuel meets EPA
burning specifications as well as marketers of used oil fuel
that process off-spec used oil fuel to produce on-spec
used oil fuel must also notify EPA. Generators of used oil
are generally exempt from notification procedures unless
they market directly to an eligible burner, thus bypassing
the marketer who would normally notify EPA.
Tracking Requirements
The tracking requirements of the rule state that all haz-
ardous waste (including characteristic waste) fuel ship-
ments must be accompanied by a manifest. For pur-
poses of tracking, off-spec used oil fuel marketers and
burners are now required to implement an invoice sys-
tem. The invoice prepared by the marketer is kept on file
for at least three years and includes such information as
name, address, and ID number of the marketer and
burner, quantity of waste being shipped, and a state-
ment on the invoice indicating that the waste is a EPA
regulated substance under 40 CFR Part 266.
All off-spec used oil marketers and burners must keep
on file for three years copies of all invoices as well as
certifications (which, briefly, is a notice from the burner
to the marketer stating that EPA has been notified, an ID
number issued, and that the burner will not use any
nonindustrial type boilers). Certifications are generally
made on the date of the initial shipment of a waste fuel.
The marketer and burner are required to keep a copy of
the certification for three years after the date of the final
shipment of a waste fuel. A marketer must keep copies
of any used oil fuel analysis that was performed to show
that a used oil is on-specification.
Hazardous Waste Fuel Defined
EPA has taken the position that any used oil in which the
total halogen content was found to be greater than 1,000
ppm will be presumed to be a hazardous waste fuel. A
generator can rebut this presumption by proving that
the high halogen levels were not the result of mixing
with a listed hazardous waste. It is important to realize
that if a listed hazardous waste is knowingly mixed with
used oil in any concentration (even if the final halogen
content did not exceed 1,000 ppm), the mixture remains
13
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USED OIL/HAZARDOUS WASTES AS FUEL
a hazardous waste unless delisted.3 The so-called "re-
buttable presumption" merely places the burden of
proving hazardous waste adulteration on EPA in cases
where the halogen limit is not exceeded.
A used oil mixed with a characteristic hazardous waste
is a hazardous waste unless it no longer exhibits that
characteristic, e.g., flash point of 140°F. Blending of a
characteristic hazardous waste/used oil mixture to ren-
der it nonhazardous is considered treatment and may
require a hazardous waste treatment permit. Off-spec
used oil, however, can be blended to meet specification
without a treatment permit.
An important implication of these regulations is the
need to carefully segregate all waste. The contamination
or mixing of used oil fuel with any of the listed solvents
may render the product a hazardous waste fuel and the
mixture will be subject to all of the regulatory require-
ments, resulting in increased handling and removal
costs.4
3At this time, used oil mixed with small quantity general (SQG)
hazardous waste is regulated as a used oil. As a practical matter,
however, such mixing is strongly discouraged because many
marketers will not accept used oil mixed with hazardous wastes.
4a) States like California can declare all used oil as a hazardous waste
subject to all the requirements for storing, treating, transporting,
and disposing of hazardous wastes.
b) Future EPA regulations are expected on the burning of hazardous
waste as fuel and off-spec oil.
14
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5. Underground Storage Tank and Hazardous
Waste Requirements
Background
Underground storage tanks (USTs) became prevalent
when industry and the public found they save space, pro-
vide protection from the environment, and prevent haz-
ards such as fires and explosions, especially for fuels, oils,
and chemicals. However, placing tanks underground does
not eliminate such problems as corrosion, structural dam-
age, and loss of product waste through leakage; thus, im-
provements have been made in tank construction and in-
stallation and in systems that measure tank inventory loss.
These improvements have not been universally adopted.
Nor have they ensured that tanks are consistently installed
properly, that safety standards are met and maintained,
and that loss of inventory and damage to the environment
are prevented. A recent EPA survey showed that the major
causes of tank failure are: 1) structural, 2) piping, 3) ancil-
lary equipment, 4) operator error, 5) external corrosion,
and 6) improper installation. Of the LIST failures, 74 per-
cent resulted in ground water contamination.
In Europe and in many states, these problems were recog-
nized early on and programs were developed to regulate
commonly used tanks such as those to store gasoline and
other petroleum products. The Federal government began
regulating tanks storing hazardous waste products as ear-
ly as 1981 under Subtitle C of the Resource Conservation
and Recovery Act of 1976 (RCRA). However, it wasn't until
November 1984 that a Federal program was established to
regulate USTs under Subtitle I of RCRA when the Hazard-
ous and Solid Waste Amendments (HSWA) were promul-
gated.
Estimates of USTs in the United States range from 1.5 to
2.5 million tanks. It is known that many USTs are leaking
or are on the verge of leaking into the environment — spe-
cifically, into our nation's ground water.
To limit or control the enormous potential risks from leak-
ing USTs, Congress directed EPA to enforce two provi-
sions of the HSWA:
(1) The requirement that owners of existing USTs notify
the states of the age, size, type, location, and uses of
their USTs.
(2) An interim prohibition on the installation of new
USTs.
The RCRA Subtitle I UST Program
As defined by EPA, a tank is a stationary device construct-
ed primarily of nonearthen materials (e.g., wood, con-
crete, steel, plastic) which provide structural support. An
UST as defined in Subtitle I is any tank or combination of
tanks, including underground piping, used to contain an
accumulation of regulated substances, the volume of
which, including underground piping, is 10 percent or
more underground. Under Subtitle I, regulated substances
include all substances defined as hazardous under the
Comprehensive Environmental Response, Compensation
and Liability Act (CERCLA) and all petroleum products, in-
cluding crude oil, and refined products, such as antifreeze.
Tanks which store hazardous wastes as defined in RCRA
are regulated under the RCRA Subtitle C hazardous waste
program. Exemptions to the Subtitle I UST definition in-
clude:
• Farm or residential tanks storing less than 1,100 gal-
lons of motor fuel for noncommercial purposes.
• Tanks storing heating oil at the premises where it is
consumed (Numbers 2,4, and 6 oil used for noncom-
mercial purposes).
• Septic tanks.
• Pipelines regulated under other laws.
• Surface impoundments, pits, ponds, or lagoons.
•. Stormwater or wastewater collection systems.
• Flow-through process tanks.
• Liquid trap or associated gathering lines directly relat-
ed to oil or gas production and gathering operations.
• Storage tanks situated on or above the floor of under-
ground areas such as basements, shafts, and tunnels.
EPA has stated that most other types of containers (for ex-
ample, small metal boxes, underground sumps, dump
tanks, hydraulic lifts, possibly even coffins and burial
vaults), could be considered USTs and as such, subject to
notification requirements.
Interim Prohibition
The interim prohibition on the installation of new tanks
applies to any tank, new or used, which was installed for
use as a UST after May 7,1985. Tanks installed after May
7,1985 must be:
a Designed to prevent releases due to corrosion or
structural failure.
• Cathodically protected against corrosion, construct-
ed of a noncorrosive material, steelclad with non-
corrosive material or its equivalent, or designed in a
manner to prevent the release or threatened release
of any stored substance.
• Constructed or lined with a material which is chemi-
cally compatible with the material stored.
These requirements may increase the total installed cost
of a tank from 20 to 100 percent over that of an unpro-
15
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UNDERGROUND STORAGE TANKS
tected steel tank; the installed cost of a double-walled
tank may be even higher.
Notification
State and Federal notification provisions were published
In the November 8,1985 Federal Register. These provi-
sions apply to all tanks regulated under RCRA Subtitle I
program:
» If a tank was taken out of operation on or before
January 1,1974 but not removed from the ground,
the owner does not have to notify the state; if a tank
was taken out of operation after January 1,1974 but
not removed from the ground, the owner must no-
tify the state by May 8,1986.
• Owners who bring any tank into operation after
May 8,1986 must notify the appropriate state or lo-
cal agency within 30 days of installation of the age,
size, type, location, and use of such tanks.
" Anyone who deposits a regulated substance in an
UST after December 8,1985 must advise the owner
or operator of the notification requirements.
" Starting 30 days after EPA issues new tank perfor-
mance standards, anyone who sells an UST must
advise the purchaser of the owner's notification re-
quirements.
Some states have regulations which are more stringent
than the Federal requirements; tank owners must con-
form to both state and Federal requirements.
The other requirements listed in RCRA Subtitle I have
not yet gone into effect. Although Congress required
EPA to have such regulations in effect by February 1987,
only draft regulations will be available at that date for
public review and comment; finalregulations will be
available by early 1988, These regulations will include:
• Leak detection and leak detection records.
• Tank technical standards (the interim prohibition
will be eliminated on promulgation).
» Performance standards on design, construction, in-
stallation, release detection, and compatibility stan-
dards.
» Corrective action for releases from tanks.
• Financial responsibility for the tank, damages from
releases, and corrective action
• Inspections, monitoring, and testing.
The CERCLA reauthorization legislation may also affect
this schedule and the contents of the final regulations.
State UST Programs
EPA intends to authorize the states to administer the
UST program in lieu of the Federal program. Once the fi-
nal regulations are promulgated, states may apply to
EPA for approval of their programs. The state program
must be at least as stringent as the existing Federal pro-
gram and must provide for adequate enforcement.
Some states have already developed UST programs, al-
though Federal regulations for authorization are not yet
in place. RCRA's Subtitle I UST program provides for
temporary authorization of such programs even though
their requirements are less stringent. If regulatory
amendments only are needed to fully comply with the
Federal program, the temporary authorization will last
one year after the Federal authorization regulations go
into effect. If legislative amendments are necessary, the
temporary authorization may last up to two years. If
both regulatory and legislative amendments are re-
quired, temporary authorization may be extended up to
three years.
Federal Enforcement of the UST Program
'Section 9006 of RCRA Subtitle I provides EPA with both
'administrative and judicial enforcement authority. EPA
,may issue a compliance order for any violation of the
provisions of the UST program. Failure to comply could
result in the issuance of an order which may include the
following penalties:
» $10,000 per tank per day for violation of the notifica-
tion and interim prohibition requirements.
« $10,000 for noncompliance with requirements of
Section 9003.
» $25,000 per day for noncompliance with an admin-
istrative order (including Section 9003(h) orders).
Additional enforcement is also available under Sections
3013 and 7003 of Subtitle C of RCRA to compel investi-
gations and to clean up spills or leaks; Section 9005 of
Subtitle I allows EPA to request information, tank test-
ing, etc. Citizen suits may be brought under Section 7002
of RCRA. There are no criminal penalties for violations
under Subtitle I.
Regulatory Development
,New regulations will affect many industrial plants, gaso-
line stations, and municipalities. The most difficult as-
pect of this program is informing the regulated commu-
nity and the public of the UST program and its
requirements. It is important that the development of
this program be monitored by those it affects to ensure
that the requirements are met. A carefully and effec-
16
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UNDERGROUND STORAGE TANKS
tively implemented program will assist in the protection
of the nation's ground water resources, especially its
critical drinking water supplies.
The RCRA Subtitle C UST Program
Existing regulations for hazardous waste tanks under
RCRA Subtitle C, Title 40 CFR Parts 264 and 265 were
amended in July 1986 and became effective in January
1987. If the amended regulation is listed in Title 40 CFR
Part 271,1(j) it becomes effective in all states on its effec-
tive date, regardless of whether the state is authorized to
operate its own program. If the regulation is not listed, it
is not effective in the authorized state until the state
amends its regulations and receives authorization from
EPA.
The regulations under Subtitle C apply as follows:
• Large quantity generators (generating over 1,000 kg
of hazardous waste per month) effective January
12,1987.
• Small quantity generators (generating between 100
and 1,000 kg of hazardous waste per month, storing
more than 180 days, or having greater than 6,000 kg
in storage), effective March 24,1987.
• Small quantity generators (generating between 100
and 1,000 kg of hazardous waste per month, storing
less than 180 days, and not having greater than
6,000 kg in storage), exempt but expected to be
added.
• All other generators are exempt.
Secondary containment can consist of an external liner,
vault, double-walled tank, or an equivalent approved de-
vice — attachments that often cannot be visually in-
spected.- All must contain the wastes. Secondary con-
tainment and monitoring requirements and their
effective dates are:
• New tanks — before they are placed into service.
• Leaking tanks — before they are returned to service.
• For existing tanks of known age, secondary contain-
ment and monitoring are required by January 12,
1989 or when the tank becomes 15 years old, which-
ever is later.
• For existing tanks of undocumented age, secondary
containment and monitoring are required by Janu-
ary 12,1989 if the facility is 15 years old or less. If
the facility is more than 15 years old, secondary
containment and monitoring are required by Janu-
ary^, 1992.
• For tanks storing chlorinated phenols, secondary
containment and monitoring are required by Janu-
ary^, 1989.
• For tanks storing newly regulated wastes, add two
years to the date when the waste becomes
regulated.
Secondary containment requirement variances are pos-
sible. The petition for variance must be either technol-
ogy- or risk-based; the petitioner must demonstrate that
an alternate design will detect leaks and prevent migra-
tion of any hazardous waste beyond secondary contain-
ment. Or, the petitioner must demonstrate that if a re-
lease occurs from an existing tank, there will be no
substantial actual or potential hazard to human health
and the environment.
Leak Detection and Closure Requirements
The leak detection system under Subtitle C must be able
to detect failure of the primary or secondary contain-
ment system or the presence of waste or liquid. Re-
sponses to leaks and spills must include:
• Prevention of further releases.
• Removal of the released waste.
a Notification to EPA. • . ...
• Repair or closure of the system.
• Certification of repair (by a professional engineer)
prior to reuse.,
Under Subtitle C closure requirements require that the
tank must be removed and all wastes and residues de-
contaminated, or the hazardous waste landfill must be
closed, and financial assurance must be provided.
Tank Assessments
The Subtitle C regulatory scheme for tanks is one of con-
tainment, detection, and response through secondary
containment, interstitial monitoring, and clean up. As-
sessments of existing tanks include a mandatory leak
test or other examination, and a written assessment of
tank integrity. Assessments of new tanks include a writ-
ten assessment of integrity, an installation inspection,
and testing prior to use.
17
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6. Clean Water Act Update
This discussion highlights recent changes in the Clean
Water Act (CWA) Reauthorization. Though the reauthori-
zation is not totally defined, this summarizes what is
likely to be enacted in areas significant to industry.
Penalties
The most substantial change in compliance enforce-
ment will be higher penalties for conviction of criminal
violations. Congress is requiring a two-to three-year jail
term and an increase in the per day penalty from
$25,000 to $50,000. Civil penalties will be increased from
$10,000 to $25,000 per day, and up to $125,000 per viola-
tion. EPA will be empowered to administer civil penal-
ties subject to hearings, thus removing the need to go to
court every time the CWA is violated.
Hazardous Waste and the CWA
In the 1986 Domestic Sewage Study, EPA estimated that
approximately 70 to 80 percent of all the hazardous
wastes that RCRA would normally control are dis-
charged to publicly owned treatment works (POTWs)
rather than put into landfills. Under the Domestic
Sewage Exemption Act, hazardous waste mixed with
domestic sewage is not treated as hazardous waste but
as domestic sewage. Hazardous wastes can be dis-
charged to the sewer directly at the plant or in more ex-
treme cases, trucked to the front of the plant and
dumped down a manhole.This has been an area of con-
cern for Congress because of the potential for uncon-
trolled discharge of hazardous waste. The CWA will con-
centrate on efforts to control RCRA substances that end
up in POTWs through more stringent pretreatment stan-
dards and by promoting the effective operation of
POTWs. Congress could decide to modify the domestic
sewage exemption if EPA and the municipalities do not
take action. Modification could have significant impact
on RCRA and CWA management and how amenable
municipalities are to treating industrial waste in the fu-
ture.
The major emphasis in the pretreatment program is now
on toxics. Initiatives are being considered that would al-
low EPA to impose biomonitoring requirements and
permit additional chemical monitoring if there were sus-
pected toxic pollutants in a particular discharge.
Pretreatment prior to discharge into a sewage system
may be required for more parameters, particularly met-
als, since POTWs traditionally have not been built to
handle large amounts of toxics.
Industrial pretreatment requirements and discharge lim-
its will be enforceable by EPA authorities even when the
local ordinances are more stringent than Federal stan-
dards.
Under the CWA amendments, EPA is now required to re-
open permits at any time for cause. For example, EPA is
required to reissue a POTW's permit with amended con-
trols if the facility's effluent is found to contain a sophis-
ticated toxic material. Previously, EPA had to wait until
the permit expired unless the permittee requested modi-
fications. The new procedure will allow EPA greater
flexibility in permitting.
Section 309F of the CWA includes a provision that al-
lows EPA to require POTWs to cut off an industrial user
whose discharge is interfering with the POTW's treat-
ment system. The statute also authorizes EPA to ask the
courts to terminate the connection if necessary. This ap-
proach has not been used often, but could also prove to
be an effective method for controlling disposal of indus-
trial waste.
CWA and Municipalities
The National Municipal Policy, aimed at encouraging
municipalities to comply with the final requirements in
their permits, could be altered under the CWA reauthori-
zation. Most municipalities have not complied with their
final current limits. Previously EPA would provide fund-
ing to aid the municipalities with compliance, but it is
now believed that the cost of managing and administer-
ing the pretreatment program, including laboratory
analyses, monitoring, and field personnel, should be
borne by the municipality. Their funding could come
from increased rates or fines imposed on out-of-compli-
ance industries. For example, if EPA requires that a mu-
nicipality build or improve a POTW to meet its final per-
mit limits, each industrial discharger could be
approached to supplement the municipality's funds.The
municipality may also request that industry reduce its
daily output, thus encouraging industry to develop its
own pretreatment systems.
Stormwater Regulations
The requirement that EPA promulgate regulations gov-
erning stormwater runoff resulted from a lawsuit filed
by the Natural Resources Defense Council several years
ago. Since then two sets of regulations have been is-
sued. Current stormwater regulations became operative
in 1984; they were slightly amended in 1985.
EPA must permit discharges; regulations are currently
being developed based on two groups of stormwater
18
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CLEAN WATER ACT UPDATE
discharges. Group I, the major and most common cate-
gory, involves stormwater generated from industrial
and manufacturing areas, including parking lots and ac-
cess roads leading to the manufacturing facility. Storm-
water transferred off the property into surface water via
pipe or other drainage system is included, and storm-
water transferred into a municipal storm sewer is likely
to be included in the proposed regulations. Group I dis-
chargers in existence prior to August 1979 now have un-
til October 1, 1990 to comply with the regulations. Dis-
chargers that came into existence after August 1979
must submit an application to EPA prior to commencing
discharge.The Group I application requires submittal of
EPA Form 1. The second part of the form requires analy-
sis of stormwater from every discharge point for the 126
EPA priority pollutants.
The Group II category includes discharges of storm-
water from parking lots of office buildings, commercial
buildings, and institutions. The deadline for these appli-
cations has been extended to October 1, 1992.
19
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7. Selecting a Responsible Transporter and
Waste Management Facility
Background
There can be little doubt that the Resource Conservation
and Recovery Act (RCRA) of 1976 places the responsibility
for the effects of hazardous waste disposal squarely on
the generator. The much touted "cradle to grave" phil-
osophy of RCRA assures that the generator is responsible
for the safe storage, transport, and ultimate disposal of his
hazardous waste. Although he will probably contract for
removal and disposal, the generator cannot assign liability
for the effects of his waste on others.
If RCRA established cradle to grave liability, then the Com-
prehensive Environmental Response Compensation and
Liability Act (CERCLA) of 1980 extended liability beyond
the grave. Under this legislation, past contributors of
wastes to sites deemed hazardous by EPA and slated for
remediation are held liable for the cleanup costs. The li-
ability is joint and several, so that it is conceivable that a
minor contributor could be saddled with a large fraction of
the remedial costs for a particular site. Furthermore, CER-
CLA imposes the potential for treble damages in cases
where responsible parties do not effectuate a timely reme-
diation of a site. Thus, a sobering picture is painted for the
hazardous waste generator. It depicts a relatively high risk
situation in which the penalties for malfeasance can be
very high. So it is imperative that the hazardous waste
generator do all in his power to ensure that his waste ma-
terials are properly handled, tracked, and disposed.
Although the risks to the generator can never be totally re-
moved, they can be managed and reduced to an accept-
able level by exercising due care in the selection of the
hazardous waste transporter and the ultimate disposal fa-
cility. This chapter discusses the selection of the transport-
er and hazardous waste management facility and hopeful-
ly gives the reader some insight into the ramifications of
these important decisions.
First consider the selection of a hazardous waste trans-
porter. Companies that offer hazardous waste transporta-
tion services range from very small local contractors to
large national corporations, and, as might be expected,
equipment and staff sophistication vary greatly. The gen-
erator then is faced with the problem of evaluating the ca-
pability and reliability of candidate transporters to fill his
need.The tools he has available to do this include certain
governmental programs and services, waste transporter
directories, professional consultants, metal finishing in-
dustry trade associations, and his own judgment.
Licensing
Hazardous waste transportation is regulated to some ex-
tent by the Federal government, and to a greater extent,
by some states. There is no Federal licensing system for
hazardous waste transporters. Under the RCRA regula-
tions a transporter is required to obtain an EPA identifica-
tion number. But the transporter does not have to demon-
strate capabilities to obtain that number. Rather, he must
simply submit a form to EPA indicating his intent to trans-
port hazardous wastes. Most regulation at the Federal lev-
el is through the Department of Transportation (DOT),
which regulates transportation of hazardous materials in
general, not specifically hazardous wastes. Many hazard-
ous wastes listed under RCRA or parallel state listings
would not necessarily be classified as hazardous under
DOT regulations. Also, DOT is concerned primarily with
acute hazards such as flammability, explosivity, and re-
lease of toxic gases; problems that would be a direct
threat to public health if an accident or spill were to occur.
The longer term or chronic environmental hazards such as
surface water or ground water contamination may not be
adequately covered by DOT provisions.
State licensing programs covering hazardous waste
transporters tend to be more responsive to the need to
establish qualifications before allowing transporters to
operate. Of course licensing procedures vary among
states and the generator is encouraged to contact the
environmental and/or transportation regulatory agen-
cies in his state to: a) find out what protective measures
are ensured through licensing provisions, and b) obtain
a listing of licensed hazardous waste transporters. Not
all states have licensing in place, but those that do typi-
cally cover such areas as equipment type and condition,
operator training, waste handling, recordkeeping, rout-
ing, emergency response, contingency planning, tariffs,
and financial responsibility or insurance. Therefore, the
fact that a transporter carries a state license gives some
assurance that his equipment meets certain standards,
that his operators are properly trained, and that he has a
contingency plan to respond to unforeseen emergen-
cies. Again, however, the generator should investigate
the requirements for licensing in his particular state
rather than assume the license itself affords adequate
protection.
Although there is no licensing at the Federal level, RCRA
does impose certain transporter requirements. The most
important of these involve the transporter's obligations
under the manifesting system. The manifest must be
completed for each shipment of hazardous waste by the
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WASTE TRANSPORTATION AND MANAGEMENT
generator. This is essentially the "chain of custody" doc-
ument that traces the waste from its point of generation
through its ultimate disposal. The transporter is required
to carry the manifest, deliver the manifest with the ship-
ment to the disposal facility, and maintain a copy of the
manifest for three years. RCRA requires the transporter
to meet delivery standards in that he is required to trans-
port the waste material to a properly permitted hazard-
ous waste management facility. RCRA further requires
that the transporter provide safe vehicle operation, have
a spill and accident reporting procedure, and that he use
appropriate materials and handling techniques for the
hazardous waste being shipped.
Selection Criteria for Transporters
Given that the Federal regulations require certain stan-
dards for transporters, there really is no direct enforce-
ment. Therefore, the generator must thoroughly investi-
gate and evaluate candidate transporters to maximize
his protection. What, then, are the factors to consider in
such an evaluation? One should begin by ascertaining
that the candidate transporter holds an EPA identifica-
tion number. Next, one should look carefully at what li-
censes and/or certifications the transporter carries. If the
state in which the generator is located has a hazardous
waste transporter licensing system, then the candidate
transporter should at least hold that license.
It is also desirable for the transporter to carry the li-
censes of the state in which the ultimate disposal facility
is located and any states he must pass through. This
may be required in some states. It is also advised that
the generator check with the issuing department to de-
termine what level of competence must be demonstrat-
ed to obtain the license.
The transporter's familiarity with the manifest system is
important. This should be evaluated by checking his re-
cordkeeping procedures, specifically that manifests are
kept on file and are readily accessed for verification of
transportation. Also, while checking company records
the accident and spill contingency plan should be in-
spected.The plan should outline emergency procedures
to be followed in the event of a spill and indicate specific
individuals and agencies to be contacted to provide
quick response and minimize potential environmental or
public health impacts.
A factor to be considered is the transporter's experience
in handling wastes from the metals finishing industry.
As a group these wastes tend to have certain character-
istics such as a high level of corrosivity, high toxic met-
als concentrations, and possibly trace concentrations of
certain toxic organic compounds, primarily solvents.
The wastes occur both in concentrated liquid form and
in solid form as dewatered sludges. It is important that
the transporter be familiar with these characteristics as
they relate to his selection of equipment, worker protec-
tion procedures, and spill contingency planning. The
generator should inspect the transporter's equipment to
be sure that it is well maintained and suited to the type
of waste to be transported.
An experienced hazardous waste transporter who has
worked with the metal finishing industry probably has
direct knowledge of the designated disposal facility. His
knowledge of that facility's practices and requirements
can be quite helpful in assuring, for example, that all
necessary waste testing has been done and that the ma-
terial is compatible with the particular facility's scope of
services. This is not to say that the generator should rely
on the transporter to evaluate the disposal facility, but
the transporter's direct experience with the designated
facility is a plus.
Two final factors to consider in evaluation of transport-
ers are reputation and cost. The transporter's reputation
can-best be established by asking for a list of references
and following through by contacting each one. In addi-
tion, the state environmental agency should be ques-
tioned concerning any reportable accidents that the
transporter may have had or any notices of violation he
may have received. Hazardous waste management fa-
cilities (HWMF) may also be able to comment on the
reputation of certain transporters.
Transportation of hazardous waste is expensive. This is
the result of a combination of factors including special-
ized equipment needs, worker training, licensing costs,
and insurance and bonding requirements. Also, hazard-
ous waste transportation is somewhat of a seller's mar-
ket as many smaller firms are being eliminated by their
inability to meet substantial financial responsibility reg-
ulations imposed by,state government. Nevertheless
there is some competition and the generator should so-
licit competitive bids after he has prequalified transport-
ers to his satisfaction.
There are several sources the generator may use to de-
velop a list of hazardous waste transporters. Published
listings of hazardous waste management firms, such as
that published by Environmental Information Ltd., list
such firms for each state. State environmental agencies
and the regional EPA offices may be accessed for lists of
licensees and firms that have been issued EPA trans-
21
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WASTE TRANSPORTATION AND MANAGEMENT
porter identification numbers. Another source is metal
finishing and chemical industry trade journals where
firms in the hazardous waste handling business fre-
quently advertise. The solid/hazardous waste industry
also has trade publications which list such firms. Finally,
consulting engineering firms are able to work with the
generator to provide possible transporters and to assure
that the transporter meets the generator's specific
needs.
Selection Criteria for HWMFs
The hazardous waste generator is faced not only with ar-
ranging for safe transportation but also for the proper
ultimate disposal of the waste. Selection of a hazardous
waste management facility (HWMF) is similar in many
ways to selection of a transporter, but longer term con-
sequences must be considered. The generator must be
satisfied that the waste will remain secure indefinitely.
Consequently, the viability of the HWMF as a business
and its ability to maintain proper operational supervi-
sion over the long term is very important.
The RCRA permitting regulations provide much more
stringent coverage for HWMFs than for transporters.
Therefore, the permitting process offers a fairly high de-
gree of assurance as to the suitability of the HWMF. All
hazardous waste treatment storage or disposal facilities
must carry an RCRA permit. This permit is issued by the
EPA, or through state environmental agencies where the
authority has been delegated by EPA.Thus the first logi-
cal place to look when developing a list of potential
HWMFs is the state environmental agency and/or re-
gional EPA office where lists of permitted facilities
should be available.
The fact that an HWMF holds an RCRA permit may not
be an absolute guarantee against future problems, but it
does indicate certain standards set forth in the regula-
tions have been met. The permit covers design, oper-
ation, and closure of the facility. The generator should
look carefully at all three when considering a facility.
The HWMF must be designed and constructed to equal
or exceed numerous criteria. For example, a secure
landfill must be sited in a proper geological setting such
that it is adequately isolated from an underlying aquifer.
This usually means at least 20 feet of low permeability
clay must be in place underthe landfill. The secure land-
fill must be lined with an impervious liner and be
equipped with a leak detection system. A leachate col-
lection and treatment system must be in place. Ground-
water monitoring wells must be installed around the
landfill perimeter. The landfill must provide separated
areas with positive barriers or different types of wastes.
Gas venting and control to prevent off-site migration is
also required. In the case of incinerators, combustion ef-
ficiency and trial burning procedures are definitely es-
tablished.
The HWMF permit also stipulates certain management
and operational practices. Testing and complete analy-
sis of all waste material entering the facility is required.
Waste handling, appropriate segregation, and worker
health and safety practices are prescribed. Extensive re-
cordkeeping is required including filing copies of all
manifests. A record of where wastes were placed in a
landfill and when they were placed must be maintained
so that such wastes could be accessed in the future if
necessary. Contingency plans to cover emergency re-
sponse and remediation of problems must be prepared
and kept readily available. Finally, ongoing ground wa-
ter monitoring, at least on a quarterly basis, is required.
A third aspect of the HWMF permit that is quite impor-
tant from the perspective of the generator's long term
security is the closure/postclosure plan. If the HWMF fa-
cility is a secure landfill, it will have a finite life. It is im-
portant at the termination of that life, that it be properly
closed to preclude the possibility.of long term environ-
mental impairment. This means at least the placement
of a proper RCRA approved cover, surface drainage, re-
vegetation, slope stability, leachate treatment, and
ground water monitoring. Financial responsibility for
postclosure coverage must be established.
Special Considerations
With respect to the metals finishing industries, there are
some special considerations in choosing an HWMF. Liq-
uids are banned from landfill disposal. Since many met-
al finishing wastes are liquid they must be solidified be-
fore they may be disposed of in a landfill. There are
various fixation and cementation processes that will so-
lidify liquid wastes and immobilize the inorganic con-
stituents such as the heavy metals. In some cases the
solidified material is sufficiently inert that it may qualify
for delisting, a formal procedure under which the mate-
rial is removed from the hazardous waste listing by EPA.
The material may then be disposed of in any permitted
municipal landfill. Some hazardous waste processors
have obtained a generic delisting whereby they process
hazardous liquid wastes from numerous generators and
produce a solid product which may be disposed of at a
conventional landfill. If presented with this option the
generator is advised to evaluate it as any other HWMF,
that is, with diligence. The processor's operation, phys-
22
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WASTE TRANSPORTATION AND MANAGEMENT
ical plant, records, and history should be carefully exam-
ined. Results of laboratory tests of the solidified product
using the generator's actual waste material should be
examined.
Candidate HWMFs should be evaluated on the basis of
physical facilities, operation, reputation, geographical
location, and cost. If possible the generator should visit
the facility to investigate the design and operational con-
siderations cited above and to review facility records.
The reputation of the HWMF, and especially any past
violations of Federal or state regulations, should be
checked. Geographical location is not the overriding fac-
tor but it is important. A nearby facility reduces the
transportation costs and decreases the possibility for
problems such as an accidental release occurring in
transit. Finally, cost must be considered. Once candidate
sites have been "prequalified" to the generator's or his
consultant's satisfaction, the least cost alternative is se-
lected. Transportation and disposal cost must be looked
at together since it may be advantageous to pay a higher
HWMF fee to dispose closer to home. The generator
should bear in mind that basing the selection solely on
cost is risky since a short term saving in disposal fees
could,result in a long term environmental impairment li-
ability of much greater magnitude.
Summary
In conclusion, it is appropriate to reiterate that Federal
and state laws place the responsibility for safe disposal
of hazardous wastes squarely on the generator. As a first
step the generator is well advised to do everything feasi-
ble to minimize the amount of waste produced. Raw ma-
terial substitutions, process modifications, reclamation
and recycle should be employed to the extent practica-
ble. When faced then with selection of a hazardous
waste transporter and HWMF, the evaluation should be
thorough and should be conducted by properly qualified
professionals. Representations should not be taken at
face value, but rather first-hand investigation should be
performed at every opportunity. The generator must
proceed with the understanding that the risk inherent in
the disposal of his waste material is his and cannot be
transferred. After implementing waste minimization the
best way he can reduce and manage that risk is through
proper screening and selection of all parties involved in
handling and disposing of his hazardous wastes.
23
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8. The Costs and Benefits of Source Reduction in
Metal Finishing
Introduction
It is not currently feasible to achieve a zero discharge of
chemical pollutants from metal finishing operations. How-
ever, substantial reductions in the type and volume of haz-
ardous chemicals wasted from most metal finishing oper-
ations are possible. Because end-of-pipe waste
detoxification is costly for small- and medium-sized metal
finishers, and the cost and liability of residuals disposal
have increased for all metal finishers, management and
production personnel may be more willing to consider
production process modifications to reduce the amount of
chemicals lost to waste.
This chapter provides guidance for reducing waterborne
wastes from metal finishing operations in order to avoid
or reduce the need for waste detoxification and the subse-
quent off-site disposal of detoxification residuals. Waste
reduction practices may take the form of:
* Chemical substitution.
" Waste segregation.
» Process modifications to reduce drag-out loss.
• Capture/concentration techniques.
Each is discussed below.
Chemical Substitution
The incentive for substituting process chemicals contain-
ing nonpolluting materials has only been present in recent
years with the advent of pollution control regulations.
Chemical manufacturers are gradually introducing such
substitutes. By eliminating polluting process materials
such as hexavalent chromium and cyanide-bearing clean-
ers, and deoxidizers, the treatments required to detoxify
these wastes are also eliminated. It is particularly desir-
able to eliminate processes employing hexavalent chromi-
um and cyanide, since special equipment is needed to de-
toxify both.
Substituting nonpolluting cleaners for cyanide cleaners
can avoid cyanide treatment entirely. For a 2 gal/min
rinsewaterflow, this means a savings of about $12,000
in equipment costs and $3.00/lb of cyanide treatment
chemical costs. In this case, treatment chemical costs
are about four times the cost of the raw sodium cyanide
cleaner.
There can be disadvantages in using nonpolluting
chemicals. Before making a decision the following ques-
tions should be asked of the chemical supplier:
• Are substitutes available and practical?
• Will substitution solve one problem but create an-
other?
• Will tighter chemical controls be required of the
bath?
• Will product quality and/or production rate be af-
fected?
• Will the change involve any cost increases or de-
creases?
Based on a survey of chemical suppliers and electro-
platers who use nonpolluting chemicals, some com-
monly used chemical substitutes are summarized in
Table 8.1.
Table 8.1 Chemical Substitutes
Polluting
Substitute
Comments
Fire Dip (NaCN
Heavy Copper
Cyanide
Plating Bath
Muriatic Acid
with additives
Copper Sulfate
Chromic Acid
Pickles,
Deoxidizers, &
Bright Dips
Chrome Based
Anti-Tarnish
Cyanide
Cleaner
Sulfuric Acid
and Hydrogen
Perioxide
Benzotriazole
(0.1-1.0%
solution in
methanol) or
water-based
proprietaries
Trisodium-
Phosphate
or Ammonia
Tin Cyanide
Acid Tin
Chloride.
Slower acting than +
H2O2 traditional fire dip.
Excellent throwing power
with a bright, smooth,
rapid finish. A copper
cyanide strike may still be
necessary for steel, zinc,
or tin-lead base metals.
Requires good pre-plate
cleaning. Noncyanide
process eliminates
carbonate build-up in
tanks.
Nonchrome substitute.
Nonfuming.
Nonchrome substitute.
Extremely reactive,
requires ventilation.
Noncyanide cleaner.
Good degreasing when
hot and in an ultrasonic
bath. Highly basic. May
complex with soluble
metals if used as an
intermediate rinse
between plating baths
where metal ion may be
dragged into the cleaner
and cause wastewater
treatment problems.-
Works faster and better
24
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COSTS/BENEFITS OF SOURCE REDUCTION
The chemical supplier can also identify any regulated
pollutants in the facility's treatment chemicals and offer
available substitutes. The federally regulated pollutants
are cyanide, chrome, copper, nickel, zinc, lead, cadmi-
um, and silver. Local and/or state authorities may regu-
late other substances, such as tin, ammonia, and phos-
phate.
Waste Segregation
After eliminating as many pollutants as possible, pollut-
ing streams should be segregated from nonpolluting
streams, Nonpolluting streams can go directly to the
sewer, although pH adjustment may be necessary. The
segregation process will likely require some physical re-
layout and/or repiping of the shop. These potentially
nonpolluting rinse streams represent about one-third of
all plating process water. Caution must be exercised to
make certain that so-called nonpolluting baths contain
no dissolved metal. The cost savings in segregating pol-
luting from nonpolluting streams is realized through
wastewater treatment equipment and operating costs.
The remaining polluting sources which require some
form of control include all dumped spent solutions, in-
cluding tumble finishing and burnishing washes, cya-
nide cleaner rinses, plating rinses, rinses after "bright
dips," and aggressive cleaning solutions.
Process Modifications to Reduce Drag-Out
Loss
Plating solution which is wasted by being carried over
into the rinsewater as a workpiece emerges from the
plating bath is defined as drag-out, and is the largest
volume source of chemical pollutant in the electroplat-
ing shop. Numerous techniques have been developed to
control drag-out; the effectiveness of each method var-
ies as a function of the plating process, operator cooper-
ation, racking, barrel design, transfer dwell time, and
plated part configuration.
Wetting agents and longer workpiece withdrawal/drain-
age times are two techniques which significantly control
drag-out. These and other techniques are discussed be-
low.
Wetting Agents
Wetting agents lower the surface tension of process
baths. To remove plating solution dragged out with the
plated part, gravity-induced drainage must overcome
the adhesive force between the solution and the metal
surface.The drainage time required for racked parts is a
function of the surface tension of the solution, part con-
figuration, and orientation. Lowering the surface ten-
sion reduces the drainage time and also minimizes the
edge effect (the bead of liquid adhering to the part
edge); thus there is less drag-out. Plating baths such as
nickel and heavy copper cyanide also use wetting
agents to maintain grain quality and provide improved
coverage. The chemical supplier should be asked if the
baths he supplies contain wetting agents and, if not,
whether wetting agents can be added. In some baths the
use of wetting agents has the potential to reduce drag-
out by 50 percent.
Longer Drain Times
With slower withdrawal rates and/or longer drain times,
drag-out of process solutions can be reduced by up to 50
percent. Where high-temperature plating solutions are
used, slow withdrawal of the rack may also be neces-
sary to prevent evaporative "freezing," which can actu-
ally increase drag-out. In the extreme case, too rapid a
withdrawal rate causes "sheeting," where huge volumes
of drag-out are lost to waste. Figure 8.1 shows the drain-
3 Sec Drag-out
O
01
15 Sec Drag-out
Horizontal
Surfaces
0 20 40 60
Elapsed Time from Withdrawal, Sec
Figure 8.1. Typical drag-out drainage rates (from Beckman Rinse Tank
Control Handbook).
25
-------
COSTS/BENEFITS OF SOURCE REDUCTION
age rates for plain and bent-shaped pieces. Drainage for
all shapes is almost complete within 15 seconds after
withdrawal, indicating that this is an optimum drain
time for most pieces.
One of the best ways to control drag-out loss from rack
plating on hand lines is to provide drain bars over the
tank from which the rack can be hung to drain for a brief
period. Hanging and removing the racks from the drain
bars ensures an adequate drain time. Slightly jostling
the racks helps shake off adhering solution.
In barrel plating, the barrel should be rotated for a time
just above the plating tank in order to reduce the volume
of dragged-out chemical. Holes in the barrels should be
as large as possible to improve solution drainage while
still containing the pieces. A fog spray directed at the
barrel or its contents can also help drag-out drainage.
Deionized water is recommended to minimize bath con-
tamination.
The combined application of wetting agents and longer
withdrawal/drainage times can significantly reduce the
amount of drag-out for many cleaning or plating pro-
cesses. For example, a typical nickel drag-out can be re-
duced from 1 liter per hour to 14 liter per hour by these
techniques.
Other Drag-Out Reduction Techniques
Rinse Elimination.The rinse between a soak cleaner and
an electrocleaner may be eliminated if the two baths are
compatible.
Low Concentration Plating Solutions reduce the total
mass of chemicals being dragged-out. The mass of
chemicals removed from a bath is a function of the solu-
tion concentration and the volume of solution carried
from the bath. Traditionally, the bath concentration is
maintained at a midpoint within a range of operating
conditions. With the high cost of replacement, treat-
ment, and disposal of dragged-out chemicals, the eco-
nomics of low concentration baths are favorable.
As an illustration, a typical nickel plating operation with
five nickel tanks has an annual nickel drag-out of about
2,500 gallons. Assuming the nickel baths are maintained
atthe midpoint operating concentration, as shown in Ta-
ble 8.2, the annual cost of chemical replacement, treat-
ment, and disposal are about $13,500. If the bath is con-
verted to the modified operating condition as shown in
the table, the annual cost of chemical replacement, treat-
ment, and disposal are approximately $12,200, a savings
of about $1,300 per year. Generally, any percent de-
Table 8.2. Standard Nickel Solution Concentration Limits
Chemical
Nickel Sulfate
NiSO4-6H2O
As NiSO4
Nickel Chloride
NiCI2-6H2O
As NiCI2
Boric Acid (H3BO3)
Con-
centration
Range
(oz/gal)
40-50
8-12
6-6.5
Midpoint
Operating
Condition
(oz/gal)
45
26.5
10
5.5
6.25
Modified
Operating
Condition
(oz/gal)
41
24.2
8.5
4.6
6.1
crease in bath chemical concentration results in the
same percent reduction in the mass of chemicals lost in
the drag-but. The disadvantage of low concentration
baths may be lowered plating efficiencies, which may
require higher current densities and closer process con-
trol. The reduction in plating chemical replacement,
treatment, and disposal costs could be partially offset by
the added labor and power costs associated with the use
of the lower concentration baths.
Clean Plating Baths. Contaminated plating baths, for ex-
ample carbonate buildup in cyanide baths, can increase
drag-out as much as 50 percent by increasing the viscos-
ity of the bath. Excessive impurities also make the appli-
cation of recovery technology difficult, if not impossible.
Low Viscosity Conducting Salts. Bath viscosity indexes
are available from chemical suppliers. As the bath vis-
cosity increases, drag-out volume also increases.
High Temperature Baths reduce surface tension and vis-
cosity, thus decreasing drag-out volume. Disadvantages
to be considered are more rapid solution decomposi-
tion, higher energy consumption, and possible dry-on
pattern on the workpiece.
No Unnecessary Components. Additional bath compo-
nents (chemicals) tend to increase both viscosity and
drag-out.
Fog Sprays or Air Knives may be used over the bath to
remove drag-out from pieces as they are withdrawn.
The spray of deionized water or air removes plating so-
lution from the part and returns as much as 75 percent of
the drag-out back to the plating tank. Fog sprays, located
just above the plating bath surface, dilute and drain the
adhering drag-out solution, thus reducing the concen-
tration and mass of chemicals lost. Fog sprays are best
when tank evaporation rates are sufficient to accommo-
26
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COSTS/BENEFITS OF SOURCE REDUCTION
date the added volume of spray water. Air knives, also
located just above the plating bath surface, reduce the
volume of drag-out by mechanically scouring the adher-
ing liquid from the workpiece. The drag-out concentra-
tion remains constant, but the mass of chemicals lost is
reduced. Air knives are best when the surface evapora-
tion rates of the bath are too low to allow additional
spray water. In some cases, use of supplementary atmo-
spheric evaporators may be justified by economic con-
siderations.
Air knives can be installed for about $500 per bath if an
oil-free, compressed air source is available. Fog sprays
can be installed for about $500 per bath if a deionized
water source is available. The spray should be actuated
only when work is in the spraying position. Properly de-
signed spray nozzles distribute the water evenly over the
work, control the volume of water Used, and avoid snag-
ging workpieces as they are withdrawn from the tank.
Proper Racking. Every piece has at least one racking po-
sition in which drag-out will be at a minimum. In gener-
al, to minimize drag-out:
• Parts should be racked with major surfaces vertical-
ly oriented.
• Parts should not be racked directly over one an-
other.
• Parts should be oriented so that the smallest sur-
face area of the piece leaves the bath surface last.
The optimum orientation will provide faster drainage
and less drag-out per piece. However, in some cases this
may reduce the number of pieces on a rack, or the opti-
mum draining configuration may not be the optimum
plating configuration. In addition, the user should main-
tain rack coatings, replace rack contacts when broken,
strip racks before plating buildup becomes excessive,
and ensure that all holes on racks are covered or filled.
Capture/Concentration with Full Reuse of Drag-Out. The
pioneer in simple, low-cost methods of reducing waste
in the plating shop was Dr. Joseph B. Kushner. In Water
and Waste Control for the Plating Shop (1972), he de-
scribes a "simple waste recovery system" which cap-
tures drag-out in a static tank or tanks for return to the
plating bath. The drag-out tanks are followed by a rinse
tank which flows to the sewer with only trace amounts
of polluting salts and is often in compliance with sewer
discharge standards. A simplified diagram of this reuse
system is shown in Figure 8.2. It is not difficult to auto-
mate the direct drag-out recovery process and commer-
cial units are available.
Evaporation
Out, > Q2
Concentrate, Concentrate
Water
Supply In,
0.2
Water
Supply In, Q,
Plating Tank Double Drag-out Tank . Flowing
- , Rinse
Tank Rinsewater
Out to
Work Sewer, Q,
Figure 8.2. Kushner method of .dpuble drag-out for full reuse.
The Kushner concept is easily applicable to hot plating
baths where the bath evaporation rate equals or exceeds
the pour-back rate, Q2. The drag-out concentration de-
pends on the bath drag-out rate, the number of drag-out
tanks, the rinsewater flow rate, Q2, the plating bath
evaporation rate, and drag-out return rate. The number
of drag-out tanks must be based on the available space.
The higher the number of counter-flowed drag-out tanks,
the smaller will be the return rate necessary to obtain
good rinsing. The Kushner multiple drag-outs are not
feasible it there is no room for the required drag-out
tanks. If there is little or no evaporation from the bath,
supplementary evaporation should be considered. Bath
contamination must be minimized by using purified (1X
or RO) water for Q2.
Capture/Concentration with Partial Reuse of Drag-Out.
By adding a trickling water supply and drain, Q3, to the
drag-out tank, the application of Kushner's concept can
be extended to other metal finishing processes which
may not be amenable to full reuse but can allow partial ,
reuse. Figure 8.3 depicts the partial reuse scheme. The
trickle concentrate can also be batch treated in a small
volume on-site, recycled at a central facility, or mixed
with Q1r for discharge, if the combined metal content is
below sewer discharge standards.
Waste Reduction Costs and Benefits
Benefits of waste reduction in the metal finishing shop
include:
B Reduced chemical cost.
27
-------
COSTS/BENEFITS OF SOURCE REDUCTION
Evaporation
Out, Qj
Water
Trickle Water Supply In,
Supply In, Qj ,,_ Q2
Concentrate
Out,
Water Supply
" In, Q,
Plating Tank
Work
Double Drag-out Flowing Rinse
Tank Tank
Trickle Rinsewater
Concentrate Out to
Out, CU Sewer, Q!
Figure 8.3. Modified method of double drag-out for partial reuse.
Table 8.3. Illustration of Cost Savings for Waste Reduction
Process chemical savings1
Copper $ 1,250
Cyanide 250
Nickel 4,000
Treatment chemical savings2
Copper 160
Cyanide 1,030
Nickel 360
Reduced treatment sludge disposal2
Copper 390
Cyanide 0
Nickel 880
Water and sewer use fee reduction3 2,250
: Total annual savings $10,570
'From Figure 8.4
2From Table 8.4 and Figure 8.4
3$1.50/1,000 gal
• Reduced water cost.
" Reduced volume of "hazardous" residuals.
» Reduced pretreatment cost.
The benefits of saving valuable chemicals and water and
reducing sludge disposal costs can best be illustrated by
an example. An electroplating operation discharges
26,000 gal/d of wastewater containing 2 pounds of cop-
per, 2.5 pounds of nickel, and 2 pounds of cyanide. The
shop can reduce its generation of cyanide and copper
waste by about 50 percent by eliminating cyanide clean-
ers and utilizing pour-back of copper cyanide solution;
generation of nickel waste can be reduced 90 percent by
pour-back of the nickel solution. Reducing wasted salts
also allows a reduced rinsewater flow rate, thus saving
water and sewer use fees. Annual dollar savings are
shown in Table 8.3.
28
Table 8.4. Chemical Costs of Treatment
and Disposal (1980 Prices)
Chemical Cost ($/lb)
Pollutant
Treatment1
Disposal2
Nickel
Copper
Cyanide
0.64
0.64
4.13
1.57
1.57
NA
'Cost of NaOH @ $0.235/lb and NaOCL @ $0.55/lb
2Cost of disposal @ $0.43/lb of sludge ($200/drum) @ 30% solids
content
—
•5 2
'
Nickel / Copper
Cyanide
3
Pollutants Discharged, Ib/d
Figure 8.4. Annual replacement cost of chemicals (1980 prices).
-------
9. Materials Reuse and Recovery
What Is Reuse/Recycling?
Direct reuse involves the reuse of a waste material without
processing either as a feedstock in a production process
or as a substitute for a commercial product. Reclamation
or recovery removes impurities and recovers raw materi-
als or by-products.
Recycling is related to the RCRA definition of solid waste
(40 CFR 261.2 (e)), i.e., materials are not RCRA solid wastes
when they can be shown to be recycled by being:
• Used or reused in an industrial process to make a
product, if the materials are not being reclaimed.
• Effective substitutes for commercial products.
• Returned to the original process from which they
were generated without first being reclaimed.
Waste streams must be physically and economically ame-
nable to recycling. Examples of waste streams generated
by the metal finishing industry not physically amenable to
recycling include:
• F006—Wastewater treatment sludges from electro-
plating operations.
• F008—Plating bath residues from the bottom of plat-
ing baths in electroplating operations where cyanides
are used in the process.
Examples of waste streams generated by the metal finish-
ing industry currently considered not economically ame-
nable to recycling include:
• F007—Spent cyanide plating bath solutions from
electroplating operations.
• F009—Spent stripping and cleaning bath solutions
from electroplating operations where cyanides are
used in the process.
• F019—Wastewater treatment sludges from chemical
conversion coating of aluminum.
Waste stream-specific factors also determine the feasibil-
ity of recycling and fall into two basic categories:
(1) Uniformity.
—Mixed wastes are difficult and costly to recycle.
—Segregation of wastes at the plant site is an'
advantage.
(2) Constituent concentrations.
—High concentrations of known constituents
increase the probability of recycling as a waste
management option.
Technologies used for reclaiming are dictated by the type
of waste and nature of contamination, and fall into two ba-
sic categories:
(1) Physical separation makes use of differences in
physical properties.
—Density and particle size (filtration, settling, floc-
culation).
—Boiling point (evaporation).
—Freezing point (crystallization).
—Solubility (solvent extraction).
(2) Chemical separation makes use of chemical reac-
tions to effect removal of certain chemical constitu-
ents.
—Precipitation.
—Oxidation-reduction.
—Ion exchange.
—Electrolytic recovery (electrochemical reactions).
Wastes Produced in Metal Finishing Operations
Primary wastes are derived mainly from two sources:
(1) Dumping of process baths and related materials
(cleaners, activators, e,tc.).
(2) Rinse waters used to wash off process solutions on
product surface or trapped in the crevices due to the
shape of the product piece.
Primary wastes and process sources are listed in Table
9.1.
A summary of raw waste data for a metal finishing oper-
ation (printed circuit board manufacturer) is shown in
Table 9.2.
Incentives for Recycle/Reuse
Case A
A plant with an existing, adequate waste treatment sys-
tem should evaluate a given recycle/reuse technology.
Savings are based on the purchase of chemical raw ma-
terials, associated waste treatment chemicals, and
sludge handling and disposal costs. If a reasonable pay-
back period on the recycle technology investment (three
years or less) is available based on these savings, then
the new system should be installed.
CaseB
A new plant, or one with an inadequate treatment sys-
tem, may present a viable economic situation for a new
recycle/reuse system. In this case an additional econom-
ic benefit is available in not spending money for unnec-
essary waste treatment capacity.
CaseC
Minimizing or eliminating generation of sludge. Justifi-
cation for recycle/reuse system is supported by possible
29
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MATERIALS REUSE/RECOVERY
Tabto 9.1. Metal Surface Finishing Wastes
Waste
Description
Spent Bath
Solution
Waste Rinse
Water
Filter Waste
Spills and
Leaks
Stripping Waste
Process Origin
Dumping of the
process solutions
after depletion or
loss of activity.
Rinsing treated
objects, equip-
ment cleaning.
quenching of
case hardened
steel.
Filtration of
process solution,
spent baths,
and treated waste
rinse water.
Overflows and
leaks from
various process
equipment
Removal of
coatings from
improperly
treated objects.
Composition
Cyanides, cyanide
complexes, hexa-
valent chrome.
copper, nickel,
zinc, cadmium.
and other
metals and their
salts in water.
Same as spent
bath solution.
Metal hydroxide
sludges, used
filter cartridges.
Same as spent
bath solution.
Cyanides, other
materials.
RCRA
Code
F007
F007
F006
F007
F009
elimination of hazardous waste residuals and therefore
minimizing long-term liability. A definitive economic
analysis is difficult in this case.
Areas of Metal Finishing Operations Where
Reuse/Recovery Technologies are of Interest:
• Recycling concentrates to process baths through
rinse tanks (most recovery schemes focus on this
area because of dragout to rinse waters).
• Nonrecycle recovery of metals or concentrates (de-
coupling of recovery process from basic finishing
process).
• Selling by-product sludges.
• Regenerating process baths.
• Recycling treated wastewaters.
Some Reuse and Recovery Technologies
More Commonly Used in Metal Finishing Industry
• Electrolytic Recovery
• Evaporation
• Ion Exchange
• Reverse Osmosis
Less Commonly Used in Metal Finishing Industry
• Carbon Adsorption
H Crystallization
• Electrodialysis
Table 9.2. Summary of Raw Waste Data - Printed Circuit
Board Manufacturing
Constituent
Total Suspended Solids
Cyanide, Total
Cyanide, Free
Copper
Nickel
Lead
Chromium, Hexavalent
Chromium, Total
Fluorides
Phosphorus
Silver
Palladium
Gold
Range (mg/l)
0.998-408.7
0.002-5.3
0.005-4.6
1.582-535.7
0.027-8.4
0.044-9.7
0.004-3.5
0.005-38.5
0.648-680.0
0.075-33.8
0.036-0.2
0.008-0.10
0.007-0.19
Electrolytic Recovery
This is a technology that uses special electroplating
equipment to lower the concentration of dissolved met-
als in discarded process baths and rinse waters. Benefits
of this technology are:
• There is no metal sludge after downstream
wastewater treatment.
• The process destroys cyanide via oxidation.
• The process permits recovery of usable metals.
• The process permits regeneration of ammoniacal or
chloride etch solutions during metal recovery.
There are three variations of electrolytic recovery in use
in the metal finishing industry:
(1) Methods primarily for removing metals from re-
30
-------
MATERIALS REUSE/R
covery rinse with minimal resulting by-product
value.
(2) Recovery of metals on high-surface area substrate
with good potential for metal by-product recovery.
(3) Electrowinning produces sheets/slabs of high pu-
rity metals with high market value. ;
Schematics of these three process variations are shown
in Figures 9.1, 9.2, and 9.3.
Drag-in
— — s
Metal
X /
Bath
Sheet,
Powder or
Mud for •«*-
Further
Processing or
Drag-out
X "
\ S \.S \ ^^Rinse
^ Water
1
Electr
Cell
*
1
Rinse
olytic i
r T T
2 1 3
* *i> i j
System
_ To Waste
" Treatment
Disposal
Drag-in Drag
— V -^
?••
Bath
i
T
Metal Depleted
Water to -*—
Waste
Treatment
i
-out
V -> v -> v ^ fc
~
HSA
Ce"
\ * \ S
k
* ^ * ~
_ Rinse
1 vtxi Water
LILT
— *»
Recovered
Electro-
chemical
Stripping
Recovered Metal
on -Fibro
us or
Porous Substrate
Chemical
Stripping
— *. Metal Sheet
Blow-down to
Waste
Treatment
— >• Disposal
or Sale
fi"c5A~l
— ^*1 1
'Cell
] 1 Recovered
' * Metal Sheet
Concentrate or Slab
for Reuse
or Sale
Figure 9.1. Electrolytic metal recovery — general purpose extractive cell
(from Lancy International, 1986).
Figure 9.2. Electrolytic metal recovery — high surface area cell
(from Lancy International, 1986).
Applications in the Metal Finishing Industry
Small electrolytic units for gold and silver recovery from
dragout rinse water have been on the market For a num-
ber of years. Only recently have these units been used
for copper, cadmium, and zinc dragout rinse water (from
cyanide baths) for base metal recovery.
New applications for this type of unit are for use on dra-
gout rinse water from acid copper, platinum, and zinc by
substituting a platinized titanium cathode for the stain-
less steel cathode normally provided with the unit. The
metal clad titanium cathocje may be subsequently used
as an anode in the electroplating process.
A commercially available unit with a 550 gph rating is
claimed to be capable of recovering gold, silver, cadmi-
um, tin, lead, zinc, and copper from cyanide bath rinse
waters. Metal recovery efficiencies are claimed to be in
the 99+ percent range. The units cost approximately
$2,000 each. These units are claimed to be easy to work
with, reasonable in cost, easy to maintain, and compact
and economical to operate for small job shops.
Drag-in
Drag-out
Rinse
Water
Bath
Slab or Sheet
:or Resale or""*
3euse as Anode17
Material
• 1
1
LSA
EMR Cell
Rinse
i
P..
System
To Waste
Treatment
Figure 9.3.. Electrolytic metal recovery — low surface area cell
(from Lancy International, 1986).
Another electrolytic unit is described by the vendor as
follows:
• Electrolytic recovery unit in operation over one year
processes 350 gal batches of spent plating baths.
31
-------
MATERIALS REUSE/RECOVERY
• Unit requires floor space of 36 inches by 20 inches.
• Has 15 to 20 square feet of area for metal recovery
and 50 or more square feet of area when used for
cyanide destruction.
• Unit costs about $6,000.
• Stainless steel anode is used in recovering cadmi-
um and zinc from spent cyanide baths.
• Platinized titanium anode is used for acid baths.
• Unit operates on 110 V; minimal electrical operating
cost.
• Typical cycle of three weeks treatment on 17 oz/gal
cyanide bath containing 6 oz/gal of cadmium metal;
achieves 2 ppm residual cyanide suitable for dis-
charge to local POTW.
Evaporation
Evaporation involves the vaporization of liquid from a
solution, slurry, or sludge using an energy source. It can
also take place without an energy source under the right
set of conditions. Evaporation is a practical process if
one component is minimally volatile (i.e., in electroplat-
ing, evaporating water concentrates the nonvolatile
metal salts). Evaporation is applicable for dragout recov-
ery from nickel, chromium, zinc, and cadmium plating.
Small atmospheric and vacuum evaporators are avail-
able for use in plating shops. Atmospheric evaporation
application involves removal of excess water from coun-
terf low rinse water before returning drag-out to the plat-
ing tank. The heat for the evaporation process can be re-
covered from the plating bath when atmospheric
evaporators are used to increase evaporative losses
from the bath. Partial recovery (with lower evaporation
rates) results in reduced heat energy cost and slower ac-
cumulation of rinse water impurities in plating tank. If all
the water needed for good rinsing can be evaporated,
then the system can be a "closed loop" with no water or
dragout going to the drain (as high as 90-99 percent re-
covery is possible with evaporation).
A schematic of the atmospheric evaporation process
adapted to plating operations is shown in Figure 9.4.
Evaporation Processes:
Single Effect Unit:
A single effect unit usually uses steam to heat the liquid
to its boiling temperature. The steam is passed through
a steam coil or jacket, and the vapors produced by the
boiling liquid are drawn off and condensed. The concen-
trated liquid is then pumped from the bottom of the ves-
sel. The process requires energy of about 1200 Btu/lb of
water evaporated. The process is illustrated in Figure
9.5.
Drag-in
Drag-out
Dl
Make-up
Water
Regenerant to
Waste Treatment
Recovered
Bath
Water Vapor
to Atmosphere
Figure 9.4- Atmospheric evaporation schematic (from Lancy
International, 1986).
Exhaust
Vacuum i
Pump
Distilled Vapor
Condensate
Steam
Steam
Condensate
Concentrated
Liquid
Transfer
Pump
Figure 9.5. Typical single-effect evaporator - falling film type
(from Metcalf and Eddy, 1985).
32
-------
MATERIALS REUSE/RECOVERY
Multiple Effect Unit:
A multiple effect unit consists of a series of single-effect
evaporators. Vapor from the first evaporator is used as
the heat source to boilliquid in the second evaporator.
Boiling is accomplished by operating the second evapo-
rator at lower pressure than the first. The process can
continue for several evaporators (effects). Depending on
the number of effects, a multiple effect unit may require
as little as 200 Btu/lb of water evaporated. The process is
illustrated in Figure 9.6.
Vapor Recompression Evaporation:
The vapor recompression evaporation process uses
steam to initially boil the liquid. The vapor produced is
compressed to a higher pressure and temperature. The
compressed vapor is then directed to the jacketed side
of the evaporator instead of using more steam, and is
thus used as a heat source to vaporize more liquid. The
vapor recompression evaporation process requires as
little as 40 Btu/lb of water evaporated. The process is il-
lustrated in Figure 9.7.
Operating Parameters
Operating costs consist of electrical power for mechani-
cal equipment on a unit (i.e., blower and pump) and heat
for evaporation. The heat needed for evaporation is 626
watts per liter or 2,371 watts per gallon.
It is necessary to minimize buildup of rinse water impuri-
ties. For example, if a high percentage of chrome dra-
gout is returned, then Cr+3 must be removed (cation ex-
change) and rinse water purified by reverse osmosis, or
deionization.
Metal Finishing Applications
Atmospheric evaporation:
Auto bumper recycler—The process consists of two
units used to recover bright nickel and hexavalent chro-
mium dragout. The brightener consumption was re-
duced by 50 percent, and the chromic acid addition was
reduced by 90 percent.
Cart maker—Process used one evaporation unit 24
hours per day, six days per week. Chromic acid addi-
tions were reduced by about 95 percent and the use of
sodium metabisulfite for waste treatment was
eliminated.
Vacuum evaporation:
Cadmium plater—The use of a cadmium cyanide plat-
ing system was able to continue with minimal use of a
Exhaust
Vacuum
Pump
Steam
Feed
Pump
Transfer
Pump
Figure 9.6.< Typical multi-effect (triple effect) evaporator — falling film type (from Metcalf and Eddy, 1985).
33
-------
MATERIALS REUSE/RECOVERY
Vent
Feed pumP
from
Feed
Tank
Dfstillate
Steam
Compressor
System
Concentrated
Brine
Pump
Distillate
Tank
Recirculation
Pump
Figure 9.7.'Vapor recompresslon application — brine concentration (from Resource Conservation Corporation, 1986).
cyanide destruct system. The anticipated payback is less
than three years.
Vapor recompression:
Electronic industry metal finisher—Able to concentrate
waste rinse water from electroplating copper foil. A 10-
fold concentration was achieved and was used as a plat-
ing bath make up.
Advantages
Evaporation is an uncomplicated, rugged, reliable, and
widely applicable process. In addition, it is comparative-
ly maintenance-free.
Disadvantages
Disadvantages include relatively high energy consump-
tion for older units. Newer designs use two stages or
heat pumps to achieve higher efficiencies. In addition,
the entire bath is recycled, including undesirable con-
stituents, and the flow rates of rinse waters must be kept
to a minimum to keep investment and energy costs
down.
Ion Exchange
Ion exchange (IX) has been a useful process in the metal
finishing industry for several decades. The most wide-
spread application is the use of cation exchange resins
to capture metal ions from a waste stream allowing their
recycle or recovery. The process is one which reversibly
exchanges ions in solution with ions retained on a reac-
tive solid material called resin.
Atypical IX system in metal finishing application has a
fixed bed of resin with the ability to exchange or remove
metallic cations or anions (chromate) from rinse waters.
Unlike other metals recovery systems, IX is almost total-
ly unaffected by dilution of the water being fed to the re-
covery unit. However, high concentrations should be
avoided. An extremely high metal capture rate is typical,
since metal discharge from the column can be less than
0.1 mg for a freshly regenerated column. Rinsing with
relatively high flow rates can be used effectively when IX
recovery of metals is utilized.
Schematics of the generic IX system for metals recycle
and nonreturn to the plating bath are shown in Figures
9.8 and 9.9.
34
-------
MATERIALS REUSE/RECOVERY
Drag-in
Drag-out
Chemical
Adjustments
Regenerant Waste
to Treatment
Make-up
Water
Figure 9.8. Ion exchange schematic — metals recycle (from Lancy
International, 1986).
Rinsewater
To Waste
Treatment
Resins Processed by In-House or Contract Refiners
or Regenerated on Tolling Basis
Figure 9.9. Ion exchange schematic — metals nonrecycle (from
Lancy International, 1986).
Process Description
The IX resins used for metals (cations) recovery are typi-
cally copolymers consisting of styrene and divihyl-
benzene in a cationic form. The IX resins for anions
(chromate) recovery are anionic form of styrene-divinyl-
benzene resin.
Generally, divalent and trivalent ions have higher affin-
ity for ion exchange than monovalent ions, i.e., divalent
cadmium, nickel cations and divalent chromate and
selenate anions are selectively removed by IX. When
useful capacity of cation exchange resins is exhausted,
they are regenerated with dilute acid solution. Metals
from the waste stream are concentrated in spent regen-
erant.
A typical process schematic of a basic two step cation-
/anion IX system including series treatment with sepa-
rate cation and anion exchange systems is shown in Fig-
ure 9.10.
Process Hardware
Pressure vessels for IX typically range in size from two
to six feet in diameter for prepackaged modular units
(i.e., to handle 25 gpm to 300 gpm flow rates) on up to a
maximum custom size of a 12 foot diameter (maximum
of 1150 gpm flow rates). The vertical height of these ves-
sels varies from six to 10 feet, providing adequate resin
storage, distribution nozzle layout, and freeboard capac-
ity for bed expansion during backwashing. The nominal
surface loading of IX vessels typically ranges from 8 to
10gpm/ft2.
Steady progress has been made in developing rugged,
reliable instruments for detection of the breakthrough of
metal ions, but even the best may be too sophisticated
for many metal finishing shops. (Reliable instrumenta-
tion is the key for producing high quality effluent for dis-
To Storage Tank or
Other Treatment Systen
Influent
Wastewater
To Storage Tank or
Other Treatment System
Backflush
Water
Acid
ffegenerant
Cation Excnange
, f System
To Storage Tank or
Other Treatment System
Backflush
Water
Treated
Wastewater
Anion Exchange
^ r System
Caustic
Regenerant
To Storage Tank or
Other Treatment System
Figure 9.10. Schematic of ion exchange (from Metcalf and Eddy, 1985).
35
-------
MATERIALS REUSE/RECOVERY
charge.) Close control of pH of feed to the IX unit is re-
quired, since lower pH tends to reduce capacity and
performance, and slightly higher values cause metal
precipitation and plugging of IX unit or its filter. Calcium
ions may cause bed plugging when sulfuric acid is used
for regeneration.
Metal Finishing Applications
Where IX is applicable for metal salt recovery, the opti-
mum approach to its use in metal finishing is to recycle
as much as possible and either sell, discard, or electro-
lytically recover that portion of the metal that cannot be
recycled to the original process.
Case Histories
Case A—Recovery of copper, nickel and chromium at a
small job shop in Montreal, Canada: IX recovery equip-
ment consists of preassembled, skid-mounted automat-
ic units. Results of the first 10 months of operation are
summarized in Tables 9.3 through 9.7. Details of operat-
ing experience with the IX system are given in the April
1986 issue of Plating and Surface Finishing magazine.
Table 9.5. Economics of Chromic Acid Recovery
Item
Sulfuric Acid (93%)
Caustic Soda (50%)
Di Water
Barium Carbonate
Electricity
Consumption
2.8kg
4.3kg
1731
0.07 kg
2 Kw-hr
Unit Cost
0.11/kg
0.22/kg
0.54/10001
0.88/kg
0.05/Kw-hr
Total
Cost/kg, $
0.31
0.95
0.09
0.06*
0.10
$1.51 /kg
*Wastewater treatment and disposal of the very toxic barium chro-
mate could significantly increase cost shown.
Table 9.6. Economics of Nickel Sulfate Recovery
Item
Sulfuric Acid (93%)
Caustic Soda (50%)
Di Water
Electricity
Consumption
0.69 kg
1.06kg
478 I
1 Kw-hr
Unit Cost
0.11/kg
0.22/kg
0.54/1000 I
0.05/Kw-hr
Total
Cost/kg, $
0.07
0.23
0.26
0.05
$0.61 /kg
Table 9.3. Performance of Recovery System Concentra-
tions in mg/1
Item
Bath
First Rinse
Third Rinse
Recovered Product
Unit Effluent
Effluent Flow (Avg.)
CrO3
260,000
170
10
53,000
20
1.61/min
Ni
84,000
460
17 .
22,000
1.3
15 l/min
Cu
82,000
260
6
35,000
0.9
10 l/min
Table 9.7. Economics of Copper Sulfate Recovery
Consumption
Sulfuric Acid (93%)
Caustic Soda (50%)
Di Water
Electricity
1.1 kg
1.7kg
981 I
1 Kw-hr
Unit Cost
0.11/kg
0.22/kg
0.54/1000 I
0.05/Kw-hr
Total
Cost/kg, $
0.12
0.37
0.53
0.05
$1.07/kg
Table 9.4. Final Plant Effluent (mg/l)
Item
Cr
Ni
Cu
Cn
PH
Flow
Actual
0.2
1.9
1.4
0.1
6.8
5
5
5
1
6-8
33-45
Limit
l/min = 11.89 gal/min
Advantages
Ion exchange is capable of extracting essentially all of
the metal from a relatively dilute feed stream; therefore,
it is the only usable recovery technology for certain ap-
plications. It can produce effluent suitable for discharge
without further treatment. Regenerants and resin rinses
must be treated. In addition, it has low capital and oper-
ating costs at a given loading rate (i.e., Ib metal/hr and
gallons per minute) compared to other recovery technol-
ogies. Costs increase, however, when regenerant chemi-
cals and wastewater treatment are considered.
36
-------
MATERIALS REUSE/RECOVERY
Disadvantages
Ion exchange is not capable of producing a highly con-
centrated stream for recycle (in actual practice, about 15-
30 gm/l vs 50 gm/l ideally). It is difficult to select the
proper split between recovered metal salts (stripped
from IX resin) and excess regenerant acid (latter is unde-
sirable in plating bath). In addition, waste containing ex-
cess regenerant must be handled.
Ion exchange is a chemically driven process (i.e., in-
creases plant chemical consumption and quantity of salt
in aqueous discharge). Sophisticated controls are re-
quired if IX resin capacity is not to be exceeded. Reliable
instrumentation to readily detect metal breakthrough is
both costly and expensive to maintain.
Reverse Osmosis
Reverse osmosis (RO) is the recovery process with the
second longest history of operation in metal finishing
(after evaporation). RO is used to separate water from
inorganic salts (metal salts). Pressure (typically 200 to
1200 psi) is used to force water from a solution through
a semipermeable barrier (membrane) which will pass
only certain components of a solution (permeate), but is
impermeable to most dissolved solids (both inorganic
and organic).
To prevent fouling of the RO membrane, feed solutions
must be pretreated to remove oxidizing materials (in-
cluding manganese, calcium, lead, and iron salts); to fil-
ter out particulates; to remove oil, grease and other film
formers; and to destroy microorganisms. RO produces a
concentrated stream for recycle to the plating bath (in-
cluding all undesirable impurities). RO performs most
efficiently on dilute rinses.
Test data on RO removal efficiencies for some metals are
shown in Table 9.8. Schematic of RO use in plating bath
recycle mode is shown in Figure 9.11.
Table 9.8. Laboratory Studies of RO Removal Efficiencies for Metals Used in Metal Finishing
Description of Study
Metal
Chromium
Copper
Lead
Nickel
Zinc
Cadmium
Chromic
Acid
Study Type
Batch
Batch
Batch
Batch
Batch
Batch
Lab,
Continuous
Flow
Waste Type
Pure compound
Pure compound
Pure compound
Pure compound
Pure compound
Pure compound
Industrial
Influent
Concen-
tration
12.5 ppm
0.94 ppm
8.65 ppm
9.35 ppm
12.5 ppm
0.7 ppm
6.5 ppm
12.5 ppm
0.95 ppm
9.3 ppm
12.5 ppm
12.5 ppm
10.0 ppm
32.8 ppm
0.10 ppm
1.0 ppm
200 ppm
Effluent
Concentra-
tion1
0.25-1.12
0.028
0.06
1.4
0.0125
0.035
0.065
0
0.005
0.205
0.87
0.25
0.375
0
0.14
0.16
0.001
0.013
30
Removal
Effi-
ciency
91-98%
97%
93%
85%
99.9%
95%
99%
100%
99.5%
97.8%
93%
98%
97%
100%
98.6%
99.5%
90%
98.7%
85%
Membrane
Type2
C-PEI
CA
CA
CA
C-PEI
CA
CA
C-PEI
CA
CA
C-PEI, pH 8
C-PEI, pH 11
C-PEI, pH 8
C-PEI, pH 11
CA
CA
CA
CA
PB
1Effluent concentration derived from influent concentration and removal efficiency.
2CA - cellulose acetate membrane; C-PEI - cross-linked polyamide membrane;
AP - aromatic polyamide membrane; PB - polybenzimidazole membrane.
Source: Metcalf and Eddy, 1985
37
-------
MATERIALS REUSE/RECOVERY
Drag-In
Drag-out
DC
Blow-down
to Wests Treatment
Dl
Make-up
Water
Figure 9.11. Revorsa osmosis schematic — recycle mode (from Lancy
International, 1986).
Process Technology
The basic components of an RO unit include:
• Membrane.
• Membrane support structure.
» Containing vessel.
» High pressure pump.
Reverse osmosis can be arranged either in parallel to
provide adequate hydraulic capacity, or in series to ef-
fect the desired degree of removal. A wide range of
flows can be accommodated depending on the number
of modules used.
Membrane Technology
Commonly used membranes include tubular mem-
branes, spiral-wound membranes, and hollow fiber
membranes.
The tubular membrane consists of a membrane which is
inserted onto or into the surface of a porous tube. This
type of membrane is primarily used for low-volume
operations.
Splrai-wound devices usually use the membrane as a
flatfilm. Sheets of the flat membrane film are separated
by a mesh spacer and are spiral wound to form a car-
tridge or module. A number of spiral tubes are usually
connected together and inserted into a pressure vessel.
Hollow fiber membranes consist of millions of aramid or
cellulose acetate fibers formed into the tube bundle or
module. The hollow fiber device permits very large
membrane areas per unit volume, making this the most
compact device in terms of surface area.
Membrane materials include cellulose acetate, aromatic
polyamides, and cross-linked polyamides. The three
types of commercial membranes are shown in Figures
9.12, 9.13, and 9.14.
Metal Finishing Applications
The largest single application of reverse osmosis is in
the recovery of nickel from nickel plating operations
(99.5 percent of RO applications in plating shops).
Factors making RO attractive for nickel recovery include:
• Valuable metal, and high volume use.
• Nickel plating baths are warm, allowing for evapo-
ration, thus permitting recycle of RO concentrate.
• pH and chemical characteristics of nickel plating
baths are favorable for RO use.
The installed cost for RO units in the plating industry
ranges from $25,000 to over $100,000. Generally, pay-
backs have been in one to two years. Maintenance usu-
ally is not a problem, providing membranes are cleaned
regularly.
Advantages
Reverse osmosis has a long-term operational history. It
uses considerably less energy than evaporation for the
same rinse water flow rate, and produces medium to
high concentrations of metal salts for recycle to plating
bath.
Product Water
Porous Support Tube Permeate Flow
with Membrane » A
.. -^r^ -* -*
•;. Brackish f
Feed Flow ^*
^:-;^^
V<-XL?.-J^i?Wsy
; .£1-.^. /
Product Water
Qk, Brine
w%'« — *- Concentrate
\>" Flow
Figure 9.12. Reverse osmosis — tubular module (from Metcalf and
Eddy, 1985).
38
-------
MATERIALS REUSE/RECOVERY
Adhesive
Permeate
Tube Bond
Feed Flow
Permeate
Flow
Feed Flow
Spiral Module
Concentrate
Flow
Concentrate
Flow ,
0-Ring' / Mesn
Membrane Spacer
Backing Material
Figure 9.13. Reverse osmosis — spiral membrane module (from
Metcalf and Eddy, 1985).
Snap
Ring
0-Ring
Seal
Concentrate
Outlet
Open Ends EP°XV
of Fibers J,t!b?, Porous
shee* Back-Up-Disc
Feed lL_i
End Plate
Fiber
Porous Feed
Distributor Tube
p-RingfPermeate
Seal End Plate
Figure 9.14. Reverse osmosis — hollow fiber module (from Metcalf and
Eddy, 1985).
Disadvantages
Reverse osmosis product cannot be highly concentrated
because of inherent technology limitations (unlike evap-
oration). Dragout impurities may be returned to the plat-
ing bath, which can be deleterious. There may not be
sufficient evaporation from the plating bath to accom-
modate the volume of RO concentrate returned, and in-
compatible materials must be removed from or chelated
in the feed solution prior to RO treatment.
Carbon Adsorption
Carbon adsorption is a separation technology used to
remove and/or recover dissolved organics and certain
inorganics from single-phase fluid streams.The material
used is granular activated carbon (GAC). Activated car-
bon includes any amorphous form of carbon that has
been specially treated (i.e., activated) to increase the
surface area/volume ratio of the carbon.
In the metal finishing industry, carbon adsorption would
be used as a polishing technology for wastewater
cleanup and recycle. In combination with optimal use of
water in plating shop, segregation of different types of
plating bath dragout, and rinsewater cleanup with acti-
vated carbon as part of treatment system, a potential for
90 to 100 percent of water reuse is available.
Carbon Adsorption Technology
The majority of carbon adsorption systems use cylindri-
cal pressure vessels which contain the activated carbon.
The stream to be treated can flow through the vessel in
an upward or downward flow design mode.The velocity
of the upward flowing stream can be set so that the car-
bon bed is expanded and fluidized or so that it is not ex-
panded. The bed expansion configuration in the GAC
system upward flow design mode allows the GAC unit
to handle influents which contain suspended solids
without appreciable pressure drop. The GAC system
downward flow design mode develops high pressure
drop with suspended solids accumulation and typically
requires upstream filtration as a pretreatment step. In
addition, the stream can flow through the beds in series
or in parallel.
The activated carbon used in the carbon adsorption pro-
cess eventually reaches a point where it will no longer
adsorb material. This spent activated carbon must then
be either regenerated or discarded. The most common
form of regeneration is thermal regeneration, although
various types of chemical regeneration are used. Chemi-
cals used for regeneration include acids, bases, and
solvents.
The amount of material removed in carbon adsorption
systems will depend on the characteristics of the pro-
cess stream and its constituents. Most carbon treatment
efficiencies are greater than 99 percent with influent
concentrations below 1,000 ppm. At higher concentra-
tions, removal efficiencies can reach 99 percent. A sche-
matic for a carbon adsorption system for chromium pol-
ishing is presented in Figure 9.15. This schematic
illustrates a parallel configured carbon adsorption
system.
Crystallization
Crystallization is the formation of solid particles within a
homogeneous phase. It occurs in a supersaturated solu-
tion where very small particles of a new phase are
39
-------
MATERIALS REUSE/RECOVERY
formed.This formation of small particles is referred to as
nucleation.The driving force behind crystallization is the
difference between the concentration of the feed and
the solubility of the solute at equilibrium temperature.
Crystallization Technology
Crystallization technology is economical when the in-
fluent stream has a relatively high concentration of salts
to be crystallized. In the metal finishing industry, the
rinse water contains relatively low concentrations of the
salts. Therefore, the rinse rate must be lowered so that
the salt concentration is raised. This process change
may have an effect on the product quality and must be
evaluated in detail. In the instances in which crystalliza-
tion is feasible, the end product is typically a reusable
caustic or acid solution, and a potentially reclaimable
metal salt or sludge. The recovery of the pickle or alkali
solution is the primary objective. However, the fact that
the reclaimed sludge may be resaleable, thus resulting
in no discharge of hazardous material, is particularly
attractive.
Commercial crystallizers may be either batch or continu-
ous operation. The main objective of crystallization
Treated
Wastewater
Carbon
Adsorption
Column
Wastowater
Containing
Chromium
ictivated
Carbon
with Adsorbed Chromium
to ba Regenerated
equipment is to produce a supersaturated solution. Cry-
stallization units may range from 10 to 40 feet in length,
and have diameters of four to 15 feet.
A schematic of a typical caustic etch regeneration sys-
tem is presented in Figure 9.16.
Applications in the Metal Finishing Industry
Fuji Sash Process
A process developed by Fuji Sash Industries of Japan for
the recovery of caustic soda (NaOH) from aluminum
etching solutions has been commercially available in the
U.S. since about 1980.
Caustic soda is recovered by continuously pumping the
etchantto a crystallization tower, where AI(OH)3 is preci-
pitated in a controlled manner. The recovered caustic
soda is then returned to the etching tank. The AI(OH)3
crystals withdrawn from the bottom of the crystallizer
are dewatered by means of a centrifuge, and the centri-
• fugate is returned to the etching tank for reuse.
The recovery operation can reduce caustic soda pur-
chases by 80 percent. The hydrated alumina crystals
produced are equivalent to commercial grade and can
be a source of income provided a market is found. How-
ever, this operation is not widely used in the U.S.
Regeneration of an acid solution for copper cleaning'is
commonly accomplished by crystallization of copper
sulfate and removal of the crystals. This process is used
by printed circuit manufacturers and metal finishers.
1 The value of the recovered copper salts justifies use of
the process.
Feed Bypass
Filtrate
Etch Tank Transfer
Pump
Filtrate
Pump
Drain
Figuro9.15. Carbon adsorption schematic (from Metcalf and Eddy,
1985).
Figure 9.16. Recovery of caustic soda from spent caustic etch (from
Metcalf and Eddy, 1985).
40
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MATERIALS REUSE/RECOVERY
EFCO Crystallization Process
The EFCO Corporation in Monett, MO uses a crystalliza-
tion process to remove dissolved aluminum from their
etch solution which can then be recycled rather than dis-
charged to a wastewater treatment plant. The system
operates continuously, producing a potentially saleable
alumina sludge (70 to 80 percent alumina) and free caus-
tic, which is reused.
Electrodialysis
Electrodialysis (ED) is a process which uses a "stack" of
closely spaced ion exchange membranes through which
ionic materials are selectively transported. The driving
force for the process (provided by voltage from a rectifi-
er) is imposed on electrodes at the two ends of the
stack.
In a plating operation, the ionic materials are extracted
from the relatively dilute recovery rinse, and accumulat-
ed in a highly concentrated stream. Concentration of
product is limited only by the volume of water transport-
ed through the membrane with the ions.The ED concen-
trate can either be recycled to the process bath or pro-
cessed separately for recovery.
A schematic of ED use in the recycle mode is shown in
Figure 9.17.
Applications in Metal Finishing
ED is being used successfully for recovering concen-
trates of gojd, silver, nickel, and tin from rinse waters. It
can be used in bright nickel plating, where the bath is
slowly circulated through the ED unit. This provides con-
tinuous removal of organic impurities and essentially ,
eliminates the need for batch purification (with associat-
ed major losses in nickel).
Advantages
Because of the high metal ion concentration available
from ED, the volume and concentration of product is sel-
dom the limitation on its capability of being returned to
the bath. Electrodialysis requires minimal amounts of .
energy. Since only ionic materials are recovered, many
undesirable impurities are rejected.
Disadvantages
Because conductivity of recovery rinse must be reason-
ably high, losses to subsequent rinsing would typically
be higher than those associated with RO or IX, but lower
than evaporation.
Drag-in Drag-out
Rinse
Water
To Waste
Treatment
Recovered
Concentrate Electrodialysis
Unit
Figure 9.17. Electrodialysis schematic — recycle mode (from Lancy
International, 1986).
Electrodialysis is a membrane process which requires
careful operation (including pretreatment) and periodic
maintenance to avoid damage to the membrane stack.
The stack is usually reconditioned by the manufacturer.
Comparison of Evaporation, RO, IX and ED
Summary of Basic Parameters for Alternate Recovery
Systems
Parameter Evaporation RO ED IX
Feed
Concentration
Product
Concentration
Capture
Efficiency
Energy .
Requirement
High
Very High
Highest
High
Low
Low
High
Medium
Medium
High
Medium
Low
Very Low
Medium
Very High
Very Low
Conclusions
A number of recycle/reuse technologies are available to
the metal finisher which offer the ability to reduce, if not
eliminate, hazardous waste generation, as well as offer the
potential for reasonable payback. Any recycle/reuse
scheme installed by a metal finisher will not necessarily
eliminate long-term liability for hazardous waste disposal.
Each technology will generate some form of waste with its
own disposal problems/requirements. Any investment
made in recycle/reuse technologies by the metal finisher
should be based (to the extent possible) on a definitive
economic analysis.
41
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10. Organic Liquids: Treatment and Residues
Management
This discussion focuses on general guidance to assist
the metal finisher in planning an organic liquids man-
agement program. While site specific concerns can have
an important impact on any hazardous waste manage-
ment program, they will be left to the development of
the facility's process team.
Why Treat?
With increasing waste disposal costs, the minimization
of hazardous materials, specifically organic liquids, is
becoming a critical issue in facility management. Only
21 states currently have hazardous waste disposal
(HWD) sites that accept hazardous waste materials. As
of August 1986 only three new licensed commercial dis-
posal facilities were under construction. Existing li-
censes for hazardous waste facilities are in jeopardy be-
cause of increased public pressure to eliminate disposal
sites from their backyard. The impending ban on solvent
disposal at HWD landfills makes it imperative that a fa-
cility implement treatment/recycle methods to minimize
solvent wastes requiring incineration. Finally, the long
term environmental liability and potential impact on the
firm's future is crucial. Hazardous waste materials im- i
properly disposed of, even if the generator acted prop-
erly, still bear liability to the generator.
Regulatory Overview
U.S. EPA has become increasingly concerned with the
total waste management of hazardous materials. Sol-
vents are an important concern since they affect all me-
dia; their usage is regulated under major environmental
legislation including the Clean Water, Clean Air, and Re-
source Conservation and Recovery (RCRA) Acts. For ex-
ample, EPA is concerned with site management where
ground water has been contaminated with organic ma-
terials.
Ground water contaminated with volatile organic com-
pounds (VOC) may be contained on site by pumping it
from the ground to an above-ground treatment system
such as an air stripping tower. Here the air flows coun-
tercurrent to the ground water and the VOC are stripped
by the air flow. The treated water is then reinjected into:
the ground or discharged to surface water or a sanitary
sewer system. The VOC-laden air may then be passed
through an activated carbon column, which adsorbs the
organic compounds from the air, thus placing it back
into the solid phase (i.e., the carbon). The carbon con-
taminated with the VOC can then be regenerated for
reuse by steam-stripping (placing the VOC into the liq-
uid phase) or disposed of via incineration, thereby oxi-
dizing and destroying the VOC. Note that all media are
affected by the VOC remedial action plan. The EPA is
concerned that we do not simply move contaminants
from one medium to another, e.g., ground water to air,
but rather look at a pollutant's total environmental im-
pact.
Organic Liquid Waste Management Program
A basic organic liquid waste management program may
consist of three steps:
(1) Assessing process wastes (chemical audit).
(2) Identifying waste management concerns.
(3) Developing waste management options.
The purpose of the process waste assessment, or
chemical audit, is to provide sufficient engineering data
to evaluate various organic waste liquid management
options in light of management limitations. The process
waste assessment tabulates such information as the
physical form of the organic chemical(s) involved, the
chemical nature of the material and possible reaction(s)
that can occur to promote or inhibit treatment, and the
process specifics on waste generation such as quanti-
ties, generation time, and temperature during time of
generation.
While this discussion deals with organic liquids, the sol-
id and gaseous phases that typically accompany liquid
waste management should also be considered. For ex-
ample, while a degreaser may contain a volatile organic
liquid compound such as 1,1,1-trichloroethane, the de-
greaser also contains chemical vapors and solids such
as metal particulates in the sump of the degreaser.
Possible reactions that the organic liquid can undergo
either in storage prior to treatment or during treatment
itself must be assessed.Typically, solvent mixtures have
beneficial reactions in that they can be separated by dis-
tillation or evaporation. On the other hand, certain or-
ganic liquids generate flammable or hazardous vapors,
and potentially explosive reactions can occur.
A complete process waste assessment must also char-
acterize each waste to the extent that its characteristics
affecttreatability. Typically, the following items need to
be reviewed:
» Solids content.
• Flammability.
• Viscosity.
• pH.
42
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ORGANIC LIQUIDS
• Temperature.
• Volatility.
• Solubility.
• Molecular weight.
• Polarity.
• Toxicity.
Metal Finishing Process Operations
Process operations involving organic compounds
should be reviewed as a starting point for determining
whether chemical substitution and/or process modifica-
tions can be introduced. Such operations, as identified
by EPA studies, include: '
• Machining—buffing compounds, rustproofing com-
pounds and machining oils.
• Cleaning and Degreasing Operations—.organicsol-
vents (depending on the oils/greases to be removed
and the substrate material processed).
• Laminating — organic resins and solvents.
" Hot Dip Coating — organic lacquers and organic
coating materials.
• Painting/Electroplating — coating systems.
• Stripping — organic and hot alkaline materials
(with organic additives).
Chemical Substitution
The audit may indicate areas where less harmful pro-
cess chemistries or those that offer recycle opportuni-
ties can be substituted to minimize hazardous waste dis-
posal costs. Chemical substitution to minimize toxic
concerns with organic solvents was initiated 50 years
ago when chlorinated solvents, with their higher solven-
cy and nonflammable nature, began to replace hydro-
carbon solvents such as gasoline, benzene, and kero-
sene. Recently, "compliance" solvents such as 1,1,1,-
trichloroethane and methylene chloride, which are i
exempt from many of the State Air Quality Implementa-
tion Plans under the Clean Air Act, are being substituted
for compounds such as perchloroethylene which con-
tribute to photochemical ozone/oxidant problems in the
urban atmosphere. Other chemicals such as the fluorin-
ated compounds are replacing certain of the chlorinated
solvents due to their higher level of acceptability under
OSHA standards.
Clean air regulations are also forcing the switch from'
low-solids to high-solids organic coating systems, and
from organic solvent-based to water-based coating sys-
tems. Hazardous waste disposal costs are also encour-
aging a second look at alkaline versus solvent paint
stripping systems.
Process Modifications
A 1981 EPA study reviewed vapor degreaser process
equipment modifications for minimizing solvent loss.
Conclusions reached were that the degreaser should be
operated in an area of relative calm, not subject to
drafts, that the freeboard ratio should be increased to 75
percent from 50 percent, that a refrigerated freeboard
chiller could reduce emission rates by 40 percent, and
that an automated lid or lid adjustment mechanism
would minimize solvent vapor layer disturbance and re-
duce solvent loss.
Other studies by EPA (September 1986) evaluated alter-
natives to organic paint strippers commonly utilized in
military applications (epoxy stripper, MS-111, which con-
tains both methylene chloride and phenol at 85 percent
and 10 percent concentrations by volume, respectively).
Chemicals containing less toxic organic materials were
successful in stripping enamels and polyamide paint
coating systems, but the two successful alternatives to
MS-111 still contained methylene chloride, although at
lower concentrations.
Other process changes for painting or coating systems
that have gained increased acceptance in the metal fin-
ishing industry include electropainting or electrocoat-
ing. These methods yield better coverage of irregular
parts including recessed areas.and sharp edges, and use
nearly 100 percent of available coating solids, thereby
minimizing organic waste liquid disposal. These sys-
tems can use aqueous-based coatings rather than halo-
genated or solvent-based coatings.
The solvent and organic wasteload from stripping im-
properly painted or coated parts and stripping racks
used to hold the parts is usually greater than from the
painting/coating process itself. Molten salt bath and
cryogenic processes can eliminate use of solvents in this
area. The molten salt bath process uses high tempera-
ture (650° to 900°F) inorganic salts without generating
toxic solvent stripping wastes. The chemical formulas
involved are:
CxHy + O2 -* XC02 + 0.5 YH2O
2 NaOH + CO2-» Na2CO3 + H20
C + 2 NaN03-> CO2 + 2 NaNO2
NaNO2 + 0.502-^NaNO3
In these formulas the organic compound (CxHy) is con-
verted into carbon dioxide (C02) and water (H2O) with
43
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ORGANIC LIQUIDS
subsequent carbonate (Na2C03) formation and return of
the nitrite salt (NaN02) to the nitrate (NalM03) form by
adsorption into the bath of oxygen from the atmos-, •
phere.The only waste from this process is the carbonate
precipitate formed, which may contain some paint pig-
ments. However, the waste is typically nonhazardous
since the organic carriers have been converted to car-
bon dioxide and water.
Another method to remove organic coating finishes
without generating solvent waste is to use very low tem-
peratures. The cryogenic process utilizes liquid nitrogen1
at -15°F to freeze and embrittle the organic finish so it
can be easily removed from the basis metal by either
wire brushing or tumbling. Residual waste consists sole-
ly of the organic finish, i.e., no added solvent chemical :
or stripping agent, and is typically nonhazardous. ;
Waste Management Concerns
After accumulating process waste data through an as-
sessment and, if possible, minimizing the quantity of or-
ganic liquids generated by either modifying the process
equipment or the process chemical, waste management
concerns should be considered. These include:
» Cost—both capital and operation and maintenance
costs.
• Complexity—different treatment systems require
different technical skill levels depending on equip-
ment involved. Complexity can be adjusted to the
level of the employees, from a manual to a fully
automated "fail-safe" system.
• Space Requirements—for the treatment system as
well as the storage of hazardous wastes prior to
transportation of either treatment residues or the .
raw waste liquids.
» Regulations Impacted—local, state and Federal.
• Treatment, Storage, Disposal Facility (TSDF) Appli-
cability—Part B forms needed?
• Long Term Environmental Liability—the firm's po-
tential exposure under the Comprehensive Environ-
mental Response, Compensation, and Liability Act
(CERCLA) should be assessed.
« Effluent Quality Requirement—according to forth-
coming EPA treatment standards for hazardous
waste treatment facilities.
» Acceptability-Public Relations—the impact of the
treatment (recycle) or storage of hazardous wastes
at the facility must be considered in light of public/
neighborhood concerns. '.
Waste Management Options
The data accumulated from the process waste assess-
ment/audit and the various site-specific and general
concerns of the facility can be used in assessing options
available to manage the hazardous organic liquids. The
three main options include off-site disposal, off-site
treatment/reclamation, and on-site treatment/reclama-
tion.
Option 1: Off-Site Disposal. Off-site disposal is the least'
favored option by U.S. EPA, although it is the easiest to
implement from the point of view of management time.
From the standpoint of long term environmental impact
and potential liability to the firm, however, it is the least
favored choice. There are no economic or regulatory in-
centives to dispose of organic liquids. The chapter on
"How to Select a Responsible Transporter and Waste
Management Facility" should be closely reviewed if this
or the next option is chosen.
Option 2: Off-Site Treatment/Reclamation. Many facili-
ties that generate hazardous organic liquids use off-site
treatment and reclamation facilities for those liquids.
The advantages and disadvantages of off-site treatment
and reclamation are:
» Low capital investment.
• Chemical reuse/chemical purchase credit.
• Quality control if raw virgin chemical rather than
reused solvent is necessary for product quality;
• Waste transportation/storage regulatory require-
ments.
• Potential liability for transport of hazardous waste
materials over public roads to the treatment site
and residues from the off-site reclamation or treat-
ment process.
Option 3: On-Site Treatment/Reclamation. More facili-
ties are turning to on-site treatment/reclamation tech-
niques to recycle organic liquids, leaving only treatment
residues for off-site disposal. Factors include:
• Initial capital funding requirements.
• Cost-benefit ratio.
• Quality control to obtain the quality of solvent or or-
ganic liquid needed for the facility's product quality
processing needs.
B Storage/treatment regulatory requirements.
• Potential liability.
• Treatment methods.
44
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ORGANIC LIQUIDS
Four methods typically used in recycling, both off-site
and on-site, include solids separation, distillation, evap-
oration, and incineration.
Solids Separation
Particle filtration is often used in the metal finishing in-
dustry to treat and extend the life of various process
electroplating baths. Similar technology can extend the
life of certain organic liquids. Particle filtration typically
removes particles of 0.5 to 100 microns. If finer particles
are affecting the reuse of the organic liquid, ultrafiltra-
tion techniques can be used to remove particles from 1
micron down to 0.001 micron.
In a particle filter, the liquid passes through a wound fil-
ter element and particles larger than the pore size are re-
tained by the filter element. As the filter element be-
comes clogged with particles, the pressure needed to
force or drive the organic liquid through the filter in-
creases until the pressure loss is too great for the pump-
ing system to maintain without forcing solids through
the filter. Then the filter must be replaced. Two major
types of particle filters are the fiber-wound element and
the fixed-pore size element.
The fiber-wound element is the standard choice for use
in recycling process baths in electroplating operations.
The pore size of the element, rated in microns, is an
"average" pore size. Since there are the same number
of diamond-shaped openings (pores) on each layer, the
openings on the outer layers must be larger due to the
increased circumference. During filtration, larger parti-
cles are therefore retained on the outer layers where the
openings are largest, while smaller particles are re-
tained selectively on succeeding inner layers of smaller
openings. The rated size of the element therefore is an
average of the largest to smallest size.
Fiber-wound elements are manufactured from various
materials at relatively low cost and are meant to be dis-
posable. The low replacement cost of the element must
take into account, however, that if it is contaminated
with a hazardous waste, it becomes a hazardous waste
itself and disposal costs will increase accordingly. That
price should be taken into account in the cost-benefit
analysis.
The fixed-pore particle filter is not used as frequently by
the electroplater.The pore size is not an average, but rel-
atively consistent throughout the filter's depth, hence
the name "fixed-pore." This filter is manufactured by
sintering (fusing), near the temperature of the alloy be-
ing used, a metal under pressure and in a reducing at-
mosphere. This causes the metal particles to bond to-
gether and form a coherent matrix which has
interconnected equal porosity. It is a relatively expen-
sive manufacturing process when compared to fiber-
wound filters. However, one advantage is that there is a
controlled pore size, not an average, and therefore it has
better solids retention for a particular size. Since it is a
metal filter it is also suitable for most solvents, and the
rigid structure of the metal matrix prevents collapse of
the openings due to high pressure applications. The
fixed-pore filter can be backwashed; therefore, there is
no need to dispose of the filter element. This minimizes
the quantity of hazardous waste generated and, over the
long term, may make it more economical than a fiber-
wound element filtration system. The cost benefit analy-
sis must be performed on the specific hazardous waste
and facility requirements.
Ultrafiltration can be used when submicron particles
must be removed from the liquid waste stream. The
membranes that make up the ultrafilter separate the par-
ticles on the basis of size, as rated by the Molecular
Weight Cut Off (MWCU). Membranes can retain from
1,000 to 1 million molecular weight compounds—rough-
ly from glucose to proteins.
The ultrafilter separates the feed stream into the perme-
ate (the liquid which passes through the filter), and the
retentate (the concentrated solids which are rejected by
the filter). In the case of electropainting or electrocoating
systems, the permeate is the water or solvent based car-
rier, while the retentate would be the solid or coatings
material returned to the bath for reuse in the coating
system.
The flux is the flow of permeate passed through the
membrane rated in gallons per square foot per day. The
concentration polarization factor is an important factor
in membrane performance affecting the flux. For an ac-
ceptable cost-benefit ratio on an ultrafilter, a high pro-
portion of flux to feed must be maintained. However, as
the solids build up at the membrane surface they cause
increased local pressures and decreased flows or flux.
Cross-flow fluid management can help to minimize the
effect of the concentration polarization by sweeping
away the accumulated layer of retained particles at the
membrane surface. Relatively high pressures are used
in cross-flow fluid management, but it is effective in sep-
arating solids and retaining relatively high flux rates.
Ultrafilters are used in the industry for reconcentrating
paint resins and pigments in spray booth washwater
and for particle separation in electrocoating systems.
45
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ORGANIC LIQUIDS
They are also used to remove oils from alkaline cleaning
solutions in order to reuse those solutions. Manufacture
of ultrafilter membranes usually includes both the plate
and frame or porous tube techniques. Porous tubes are
bound together to form bundles in a fabricated ultrafilter
module, while the plate and frame membranes are
rolled to form a spiral module construction.
Distillation
Distillation is one means of reclaiming organic liquids
such as solvents. Organic solvents contaminated with
oils and greases from the degreasing process will exhib-
it a wide boiling point differential between the solvents :
and the contaminants. Distillation uses this differential
to separate the compounds; i.e., the solvent vaporizes at
a relatively low temperature compared to the oil/grease
contaminants.
Although considerable energy is required for distillation,
solvents do vaporize at a relatively low temperature
compared to water (100 Btu/lb versus 980 Btu/lb). There-
fore, the energy required to evaporate water-based liq-
uids is significantly lower, and the cost balance is usual-
ly favorable. Where large volumes of solvents require
distillation, vacuum systems may also be applied to fur-
ther decrease the energy requirements.
Distillation is applicable to a wide variety of spent sol-
vents used in the metal finishing industry—both haloge-
nated and nonhalogenated compounds, such as the
spent methyl ethyl ketone solvent mixture from a paint
line clean-out. Continuous distillation columns which
contain trays, packing, plates, etc. can be used to in-
crease the liquid vapor contact area for larger volume re-
quirements. Smaller units very similar in construction to
the familiar vapor degreaser are typically used in the
metal finishing industry. The main difference between a
solvent still versus a vapor solvent degreaser is the high-
er temperature needed to operate the still. These smaller
batch stills typically allow for on-site recycling for all but
the smallest volume users. (State regulations should be
closely checked to insure that recycling is properly per-
mitted at the state level.) A recent EPA project summary
identified a distillation unit capable of handling as little
as 14to 35 gallons of a solvent per batch. Others have in-
dicated that solvent usage of only 5 gallons per batch
could be handled. These smaller units can even be table
top mounted, while most larger units can be mounted
within 10 to 20 square feet of floor space.
Of concern in distillation are azeotrophic mixtures, i.e.,
liquid mixtures that exhibit a maximum or minimum
boiling point relative to the boiling points of the sur-
rounding mixture composition. The boiling points of the
pure components must be sufficiently close to permit
the formation of an azeotrope. These mixtures are not
formed when dealing with the typical solvent and oil/
grease mixtures encountered in the metal finishing in-
dustry. Solids in feed, another concern, may plug the
packing in a larger distillation column and need to be fil-
tered prior to off-site reclamation. Solids are not a prob-
lem on the smaller on-site batch units since they will re-
main in the bottom residue of a still.
A batch still at a metal finishing facility which has a feed
stock of spent solvents contaminated with oils, con-
densed water, and solids can satisfactorily recycle sol-
vents back to the metal finishing process vapor de-
greaser. A typical example:
• Feed Stock - solvent 90-95%/oils, water 5-10%/solids
0-1%.
• Distillate - solvent 95-99%/oils, water 1-5%,
• Bottoms - oils, water 85-95%/solids 5-10%/solvents
1-5%.
Evaporation
In distillation all or most of the liquid phase components
have an appreciable vapor pressure and therefore ap-
pear in the overhead vapors. In evaporation the over-
head vapor is primarily solvent (e.g., water), contaminat-
ed only by smaller amounts of liquid phase material
(organic or inorganic solids with very low vapor pres-
sures at the temperature of evaporation), which are
called entrainments.
In wiped film evaporation (WFE) a rotating arm wipes a
thin film of solvent across the evaporative surface. There
is very little hydraulic head to impede equilibrium vapor
pressures, and therefore a high heat efficiency is
achieved. WFE is also useful to reclaim solvents that
contain a higher quantity of solids since the mechanical
wiping action of the rotating arm moves the solids
across, rather than allowing them to adhere to the evap-
orative surface. While WFE is relatively expensive com-
pared to batch stills, because of the critical machining in-
volved in the wiped film surface, they are considered
state-of-the-art technology and useful for gaining the
higher recovery of solvents.
A WFE can typically handle higher solids content in the
feed stock as indicated in the example:
• Feed Stock - solvent 70-95%/oils, water 5-15%/solids
0-35%.
46
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ORGANIC LIQUIDS
Distillate - solvent 97-99%/oils, water 0-3%.
Bottoms - solids 30-65%/oils, water 35-65%/solvent
0-5%.
incineration
Incineration is used to detoxify and sterilize compounds.
While there is energy to recover from certain organic liq-
uids, spent halogenated solvents usually do not yield
sufficient quantities to make them marketable. Incin-
eration is primarily used with degreaser and still bottom
sludges which may require mixing with a high heating
value fuel oil to be effective. Organic wastes composed
of carbon and hydrogen have a relatively high heating
value. However, when halogenated compounds are add-
ed to the organic wastes, their energy content drops sig-
nificantly. For example, carbon has 14,000 Btu/lb of en-
ergy content, while hydrogen has 61,000 Btu/lb energy
content. Ethane contains about 22,000 Btu/lb, and the
heating value drops when chlorine atoms are added.
Subsequent heating values of the compound are:
a Dichloroethane - 5,400 Btu/lb.
a Trichloroethane - 3,600 Btu/lb.
» Tetrachloroethane - 2,500 Btu/lb.
^Certain organic liquids contain significant heating fac-
tors such as methyl ethyl ketone (20,000 Btu/lb), toluene
(18,000 Btu/lb), and various phenol based stripping com-
pounds (13,000 to 15,000 Btu/lb).
The heat content of the fuel is important in determining
whether EPA considers it a hazardous waste fuel that is
burned for energy recovery in a boiler or industrial fur-
nace. The EPA "rule of thumb" is that it must have great-
er than 5,000 Btu/lb. Currently a hazardous waste fuel is
exempt from regulations when burned in an industrial
furnace. However, hazardous wastes, if burned, are reg-
ulated under RCRA hazardous waste incineration stan-
dards. Therefore, the fuel content is an important factor
in regulatory involvement. It is important to keep in
mind that chlorinated solvents generally fall below this
5,000 Btu/lb value and therefore are not considered haz-
ardous waste fuel.
treatment. In the case of particle filtration, the spent fil-
ter elements could increase this volume significantly.
Distillation. The bottoms—the resultant oil/water mix-
ture that is removed from the solvent during distilla-
tion—are considered hazardous and must be handled
appropriately. Typically these wastes are incinerated.
Evaporation. Similar to the distillation column, the
wiped film evaporator will generate bottoms which are
considered hazardous when dealing with organic liq-
uids.
Incineration. The incinerator ash generated from com-
bustion may contain hazardous constituents. EPtoxicity
testing to determine the leachate values of the metals
corning from the ash will depend on the content in the
feed steam to the incinerator. While organic solvents will
typically be burned with no residual, contributors to the
incinerator may make the resultant "mixed" ash hazard-
ous.
In the case of the residuals discussed, potential environ-
mental liability is still incurred by management even if
the waste has been sent off-site for reclamation. There-
fore, the feasibility of additional treatment operations
should be investigated with the specific hazardous
waste treatment facility.
Management options for treatment process residuals in-
clude:
« Incineration.
• Off-site disposal in secure landfills (depending on
the outcome of the recent EPA provision).
• Additional treatment to reduce volumes, such as re-
distillation of the bottoms from a distillation col-
umn by using steam stripping techniques.
Treatment Process Residuals
Solids separation. Particle filtration as well as ultrafiltra-
tion removes solids from hazardous organic liquids. If
any of the organic liquids are retained on the solids, or if
the solids themselves constitute hazardous waste ac-
cording to EP toxicity testing or similar characterization
under RCRA, these residuals may require further off-site
47
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11. Characterization and Treatment of
Aqueous Wastes
This chapter provides an overview of technologies appli-
cable to treatment and management of residues result-
ing from metal finishing. It is based on experience over
the past five years in over 100 facilities processing met-
als from the point at which they are mined to the point at
which they are sold as finished products.
Regulatory History of RCRA
It is first appropriate to review the regulatory history of
RCRA to develop a proper framework under which ap-
propriate management and treatment of residues will
occur. In November 1984, Congress amended the Re- ;
source Conservation and Recovery Act (RCRA) of 1976
by passing the Hazardous and Solid Waste Amend-
ments (HSWA). Central to these amendments was a
hierarchy of waste management (see Figure 11.1). It was
Congress' intent to place an emphasis on source reduc-
tion, material reuse and recovery, and treatment and to
strongly de-emphasize land disposal.
Source Reduction
Material Reuse and Recovery
Treatment
Land Disposal
Figure 11,1. HSWA hierarchy.
Earlier chapters of this document reviewed effective
control technologies for source reduction and material
reuse and recovery. In chapter 10, applicable technol-
ogies were presented for treatment of organic and spent
solvent wastes. The emphasis of this chapter is on three
other types of wastes generated by metal finishers.
These are:
» Corrosive wastes. ;
• Cyanide containing wastes. ]
» Metal containing wastes.
The emphasis of the hierarchy created by Congress un->
der HSWA will yield:
« More concentrated wastes.
• Wastes with a varied array of constituents.
• Wastes with a greater degree of complexation.
One obvious consequence of the emphasis on source
reduction and material reuse and recovery is that the
wastes generated for treatment will be more concentrat-
ed. As these wastes are concentrated, constituents pres-
ent at non-detectable concentrations in dilute wastes
will be present at elevated, treatable concentrations.
Likewise, the degree of complexation will become great-
er as the wastes become more concentrated.
Waste Characterization
One of the most critical steps in ensuring proper selec-
tion of source reduction, material reuse and recovery,
and treatment alternatives is effective waste character-
ization. Specifically, this means full characterization of
each source of waste generated in a facility and docu-
mentation of the rate at which each waste is generated.
Additionally, for each constituent that is present at ele-
vated concentrations, it is important to understand the
reasons for their presence. Detailed characterization will
yield a better basis for design, a better basis for oper-
ation, and better data for use in negotiating permit con-
ditions with regulatory authorities.
Many of the technologies which are applicable to the re-
sidues of metal finishing processing have their roots in
wastewater treatment. There are many fine descriptions
of these technologies when applied to wastewater in the
literature. The emphasis of this chapter will be on the
applicability of these technologies to the treatment of
wastes.
Waste Segregation
The first step to be taken in establishing a treatment sys-
tem design or modification is to determine which wastes
require segregation. The objective of segregation is to
minimize the amount of reagent required for treatment
and the size of treatment vessels, and to maximize treat-
ment removal effectiveness.
This chapter will concentrate on four categories of
wastes requiring segregation:
• Cyanide containing wastes.
« Chromium (VI) containing wastes.
• Arsenic and selenium containing wastes.
• Other metals containing wastes.
Segregation must be viewed in conjunction with neu-
tralization. The most effective means of treating a corro-
sive waste is through neutralization. Neutralization is
the reaction of an acid or base with a corrosive waste to
reduce or eliminate the corrosivity. The definition of a
corrosive waste under RCRA is a waste with a pH less
than or equal to 2.0 or a pH greater than or equal to 12.5
(note: it is also defined as a waste that corrodes steel
48
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AQUEOUS WASTES
(SAE 1020) at a rate in excess of 6.35 millimeters per
year). As such, neutralization in the context of treating a
RCRA waste means the addition of a base to raise the pH
to above 2.0 or an acid to lower the pH to below 12.5.
Neutralization
One technique used in a number of facilities that utilize
molten salt for metal surface treatment prior to pickling,
is to take advantage of the alkaline values generated in
the molten salt bath in treating other wastes generated
in the plant. When the bath is determined to be spent, it
is in many instances manifested, hauled off-site, and
land disposed. One technique is to take the solidified
spent molten salt (molten salt is sold at ambient tem-
peratures) and circulate acidic wastes generated in the
facility over the material prior to entry to the waste
treatment system. This in effect neutralizes the acid
wastes and eliminates the requirements of manifesting
and land disposal.
Cyanide Containing Wastes
There are six methods applicable to the treatment of
cyanide wastes for metal finishing:
Alkaline chlorination.
Electrolytic decomposition.
Ozonation.
UV/Ozonation. "
Hydrogen peroxide.
Ferrous sulfate precipitation.
Alkaline chlorination is the most widely applied in the
metal finishing industry. A schematic for cyanide reduc-
tion via alkaline chlorination is provided in Figure 11.2.
This technology is generally applicable to wastes con-
taining less than one percent cyanide, generally present
as free cyanide. It is conducted in two stages; the first
stage is operated at a pH greater than 10 standard units
and the second stage is operated with a pH in the range
of 7.5 to 8 standard units. Alkaline chlorination is per-
formed using sodium hypochlorite and chlorine.
Electrolytic decomposition technology was applied to
cyanide containing wastes in the early part of this cen-
tury. It fell from favor as alkaline chlorination came into
use at large-scale facilities. However, as wastes become
more concentrated, this technology may find more wide
spread application in the future. The reason being that it
is applicable to wastes containing cyanide in excess of
one percent. The basis of this technology is electrolytic
decomposition of the cyanide compounds at an elevated
temperature (200°F) to yield nitrogen, C02, ammonia,
and amines (see Figure 11.3).
Ozonation treatment can be used to oxidize cyanide,
thereby reducing the concentration of cyanide in
wastewater. It has not found widespread application in
the metal finishing industry, however, because it gener-
ally has higher capital and operating costs than alkaline
chlorination. Additionally, in most instances ozonation
is no more effective in reducing cyanide concentrations
than alkaline chlorination.
NaCN + CI2—CNCI + NaCI
CNCI + 2 NaOH^NaCNO + H20
2 NaCNO + 3 CI2 + 4NaOH-<-2 CC
NaOCI
or
CI2
2 + 6 NaCI+2 H20
NaCN
Cyanide Bearing
Waste
• <1% CN
• Free CN
NaCNO
NaOCI
or
Cl,
C02
1 I *-H20
f—TTTT NaCI
pH>10s.u.
ORP 350-400mv
7.5
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AQUEOUS WASTES
One interesting variation on ozonation technology is
augmentation with UV radiation. This is a technology
that has been applied on wastes in the coke by-product
manufacturing industry. A significant development has
been rnadethat has resulted in significantly less ozone
consumption through the use of UV radiation (see Fig-
ure 11.4).
Cyanide reduction with hydrogen peroxide is effective in
reducing cyanide. It has been applied on a less frequent
basis within this industry, due to the fact that there are
high operating costs associated with hydrogen peroxide
generation. The reduction of cyanide with peroxide oc-
curs in two steps and yields C02 and ammonia (see Fig-
ure 11.5).
Each of the technologies described above is effective in
treating wastes containing free cyanides; that is, cyan-
ides present as CN" in solution. There are instances in
metal finishing facilities where complex cyanides are
present in wastes. The most common are complexes of
iron, nickel, and zinc. A technology that has been applied
to remove complex cyanides from aqueous wastes is
ferrous sulfate precipitation. The technology involves a
two-stage operation in which ferrous sulfate is first add-
ed at a pH of 9 to complex any trace amounts of free cya-
nide. In the second stage, the complex cyanides are prer
cipitated through the addition of ferrous suifate or ferric
chloride at a pH range of 2 to 4. i
NaCN +• Oj •* NaCNO + O2
NaCNO+Oj —N2+C02
Ozonation with UV Radiation
UV Absorption — Ozone and Cyanide Are Raised
to Higher Energy States
— Free Radicals Are Formed
— More Rapid Reaction
— Less Ozone Required
Figure 11.4. Cyanlda reduction via ozonation.
NaCN + Hj02 - NaCNO + H20
NaCNO + HjO — C02+NH3+NaOH
Chromium Containing Wastes
There are three treatment methods applicable to wastes
containing hexavalent chromium. Wastes containing tri-
valent chromium can be treated using chemical precipi-
tation and sedimentation, which is discussed below. The
three methods applicable to treatment of hexavalent
chromium are:
B Sulfur dioxide.
• Sodium metabisulfite.
• Ferrous sulfate.
Hexavalent chromium reduction through the use of sul-
fur dioxide and sodium metabisulfite has found the wi-
dest application in the metal finishing industry. It is not
truly a treatment step, but a conversion process in
which the-hexavalent chromium \s converted to trivalent
chromium. The hexavalent chromium is reduced
through the addition of the reductant at a pH in the
range of 2.5 to 3 with a retention time of approximately
30 to 40 minutes (see Figure 11.6).
Ferrous sulfate has not been as widely applied. Howev-
er, it is particularly applicable in facilities where ferrous
sulfate is produced as part of the process, or is readily
available. The basis for this technology is that the hexa-
valent chromium is reduced to trivalent chromium and
the ferrous iron is oxidized to ferric iron.
Arsenic and Selenium Containing Wastes
It may be necessary to segregate waste streams con-
taining elevated concentrations of arsenic and selenium,
especially waste streams with concentrations in excess
SO2 + H2O-» H2S03
H2Cr04 + 3H2S03 -* Cr2(S04)3
S02
pH2.5-3.0s.u.
30 Minutes Retention
Figure 11.6. Cyanide reduction via hydrogen peroxide.
! Figure 11.6. Hexavalent chromium reduction.
50
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AQUEOUS WASTES
of 1 mg/l for these pollutants. Arsenic and selenium
form anionic acids in solution (most other metals act as
cations) and require special preliminary treatment prior
to conventional metals treatment. Lime, a source of cal-
cium ions, is effective in reducing arsenic and selenium
concentrations when the initial concentration is below 1
mg/l. However, preliminary treatment with sodium sul-
fide at a low pH (i.e., 1 to 3) may be required for waste
streams with concentrations in excess of 1 mg/l. The sul-
fide reacts with the anionic acids to form insoluble sul-
fides which are readily separated by means of filtration.
Chemical Precipitation and Sedimentation
The most important technology in metals treatment is
chemical precipitation and sedimentation. It is accom-
plished through the addition of a chemical reagent to
form metal precipitants which are then removed as so-
lids in a sedimentation step. The options available to a
facility as precipitation reagents are: lime (Ca(OH)2),
caustic (NaOH), carbonate (Ca(C03)2 and Na(CO3)2), sul-
fide (NaHS and Fe2S), and sodium borohydride (NaBH4)
(see Figure 11.7).
Lime (Ca(OH)z)
Caustic (NaOH)
Carbonate (Ca(CO3)z and Na(C03)2)
Suifide (NaHS and FE2S)
Sodium Borohydride (NaBH4)
Combined
Figure 11.7. Metal wastes chemical precipitation and sedimentation.
The advantages and disadvantages of these reagents
are summarized in Figure 11.8. Lime is the least expen-
sive reagent, however it generates the highest volume
of residue. It also generates a residue which cannot be
resold to smelters and refiners for reclaiming because of
the presence of the calcium ion. Caustic is more expen-
sive than lime, however it generates a smaller volume of
residue. One key advantage to caustic is that the result-
ing residues can be readily reclaimed. Carbonates are
particularly appropriate for metals where solubility with-
in a pH range is not sufficient to meet a given set of treat-
ment standards. The sulfides offer the benefit of achiev-
ing effective treatment at lower concentrations due to
Lime
Least Expensive Precipitation Reagent
Generates Highest Sludge Volume
Sludges Generally Can Not Be Sold to Smelter/Refiners
Caustic
More Expensive than Lime
Generates Smaller Volume of Sludge
Sludges Can Be Sold to Smelter/ Refiners
Carbonates
« Applicable for Metals where Solubility
within a pH Range Is Not Sufficient to Meet
Treatment Standards
Figure 11.8. Applicability of reagents.
lower solubilities of the metal sulfides. Sodium borohy-
dride has application where small volumes of sludge
that are suitable for reclamation are desired.
It is appropriate to look at reagent use in the context of
the current regulatory framework under HSWA. Histori-
cally, lime has been the reagent of choice. It was rela-
tively inexpensive and simple to handle. The phrase
"Lime and Settle" refers to the application of lime pre-
cipitation and sedimentation technology. In the 1970s,
new designs made use of caustic as the precipitation
reagent because of the reduction in residue volume real-
ized and the ability for reclamation. In the 1980s, a return
to lime and the use of combined reagent techniques
have come into use.
One obvious question is why return to lime as a treat-
ment reagent, given that caustic results in a smaller resi-
due volume and a waste that can undergo reclamation?
The answer lies in the three points discussed above, that
result from the implementation of the HSWA hierarchy.
As source reduction and material reuse and recovery
techniques are applied, facilities will be generating:
• More concentrated wastes.
• Wastes with a varied array of constituents.
• Wastes with a greater degree of complexation.
Complexation
Complexation is a phenomenon that involves a coordi-
nate bond between a central atom, the metal, and a li-
gand, the anions (refer to Figure 11.9). In a coordinate
bond, the electron pair is shared between the metal and
the ligand. A complex containing one coordinate bond is
51
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AQUEOUS WASTES
Motal — Central Atom
Anions — Ugands
Coordinate
Bond
Electron Pair
Is Shared
Ono Coordinate Bond — Monodentate
Multiple) Coordinate Bonds — Polydentate — Chelates
Examples: Monodentate Ammonia
Chelate Oxalates (Bidendate)
EDTA (Hexadentate)
FIguro 11.9. Complexation.
referred to as a monodentate complex. Multiple coordi-
nate bonds are characteristic of polydentate complexes.
Polydentate complexes are also referred to as chelates.
An example of a monodentate forming ligand is ammo-
nia. Examples of chelates are oxylates (bidentates) and
EDTA (hexadentates). :
The reason for the return to lime is due to the calcium
ion present in lime. The calcium ion present in solution
through the addition of lime is very effective in compet-
ing with the ligand for the metal ion. The sodium ion
contributed by caustic is not effective. As such, lime dra-
matically reduces complexation and is more effective in
treating complexed wastes. The term "high lime treat-
ment" has been applied in cases where excess calcium
ions are introduced into solution. This is accomplished
through the addition of lime to raise the pH to approxi-
mately 11.5 or through the addition of calcium chloride
(which has a greater solubility than lime).
The use of combinations of precipitation reagents has
been most effective in taking advantage of the attributes
of caustic as well as the advantages of lime. As an exam-
ple, a system may use caustic in a first stage to make a :
coarse pH adjustment followed by the addition of lime to
make a fine adjustment. This achieves an overall reduc-
tion in the sludge volume, through the use of the caustic
and more effective metal removal through the use of
lime. Sulfide reagents are used in a similar fashion in
combination with caustic or lime to provide additional
metal removal, due to the lower solubility of the metal
sulfides. Sulfides are also applicable to wastes contain-:
ing elevated concentrations (i.e., in excess of 2 mg/l) of
selenium and arsenic compounds.
Other Metals Wastes
There are three techniques applicable to managing so-
lids generated in metal finishing. These are:
• Dewatering.
• Stabilization.
• Incineration.
There are four dewatering techniques that have been
applied in metal processing. The most widely applied
techniques are vacuum and belt filtration. They have a
higher relative capital cost but generally have a lower
relative operating cost. Plate and frame filter presses
have experienced less wide spread application. Belt fil-
ters generally have a lower relative capital cost and have
higher relative operating costs. The higher operating
costs are due to the fact that the units are more labor in-
tensive. Centrifuges have been applied in specific in-
stances, but are more difficult to operate when a widely
varying mix of wastes is treated.
Experience has shown that companies are most suc-
cessful in applying a dewatering technique that they
have successfully designed and operated in similar ap-
plications within the company. As an example, many
companies operate plate and frame filter presses as a
part of metal manufacturing operations. The knowledge
gained in metal processing had been successfully trans-
ferred to treatment of metal finishing wastes.
There are six stabilization techniques currently avail-
able, however, only two of them have found wide
spread application. These are cementation and stabiliza-
tion through the addition of lime and fly ash. There is
currently developmental work being undertaken to
make use of bitumen, paraffin, and polymeric materials
to reduce the degree to which metals can be taken into
solution. Encapsulation with inert materials is also un-
der development.
52
U. S. GOVERNMENT PRINTING OFFICE 1987/748-121/67040
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