&EPA
United States
Environmental Protection
Agency
Risk Reduction
Engineering Laboratory
Cincinnati, OH 45268
Research and Development
EPA/600/S-92/058 October 1992
ENVIRONMENTAL
RESEARCH BRIEF
Waste Reduction Activities and Options for a
Scrap Metal Recovery Facility
Hanna Saqa and Daniel J. Wans*
Abstract
The U.S. Environmental Protection Agency (EPA) funded a project
with the New Jersey Department of Environmental Protection and
Energy (NJDEPE) to assist in conducting waste minimization as-
sessments at 30 small- to medium-sized businesses in the state of
New Jersey. One of the sites selected was a facility that processes
scrap metal to recover refined metals for reuse. The facility concen-
trates on recovery of tungsten, molybdenum, and tantalum. The
processes used by the facility involve washing, decreasing, me-
chanical cleaning, and acid treatment. A site visit was made in 1990
during which several opportunities for waste minimization were
identified. Options identified include improved process pH control,
changes in solid precipitation technology, and acid reuse. Implemen-
tation of the identified waste minimization opportunities was not part
of the program. Percent waste reduction, net annual savings, imple-
mentation costs and payback periods were estimated.
This Research Brief was developed by the Principal Investigators
and EPA's Risk Reduction Engineering Laboratory in Cincinnati,
OH, to announce key findings of this completed assessment.
Introduction
The environmental issues facing industry today have expanded
considerably beyond traditional concerns. Wastewater, air
emissions, potential soil and groundwater contamination, solid
waste disposal, and employee health and safety have become
increasingly important concerns. The management and dis-
posal of hazardous substances, including both process-related
wastes and residues from waste treatment, receive significant
attention because of regulation and economics.
* New Jersey Institute of Technology, Newark, NJ 07102
As environmental issues have become more complex, the strate-
gies for waste management and control have become more sys-
tematic and integrated. The positive role of waste minimization and
pollution prevention within industrial operatbns at each stage of
product life is recognized throughout the world. An ideal goal is to
manufacture products while generating the least amount of waste
possible.
The Hazardous Waste Advisement Program (HWAP) of the Divi-
sion of Hazardous Waste Management, NJDEPE, is pursuing the
goals of waste minimization awareness and program implementation
in the state. HWAP, with the help of an EPA grant from the Risk
Reduction Engineering Laboratory, conducted an Assessment of
Reduction and Recycling Opportunities for Hazardous Waste (AR-
ROW) project. ARROW was designed to assess waste minimization
potential across a broad range of New Jersey industries. The
project targeted 30 sites to perform waste minimization assessments
following the approach outlined in EPA's Waste Minimization Op-
portunity Assessment Manual (EPA/625/7-88/003). Under contract
to NJDEPE, the Hazardous Substance Management Research
Center at the New Jersey Institute of Technology (NJIT) assisted in
conducting the assessments. This research brief presents an as-
sessment of the processing of scrap metal to recover refined metals
(1 of the 30 assessments performed) and provides recommendations
for waste minimization options resulting from the assessment.
Methodology of Assessments
The assessment process was coordinated by a team of techni-
cal staff from NJIT with experience in process operations,
basic chemistry, and environmental concerns and needs. Be-
cause the EPA waste minimization manual is designed to be
primarily applied by the inhouse staff of the facility, the degree
of involvement of the NJIT team varied according to the ease
with which the facility staff could apply the manual. In some
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cases, NJfTs role was to provide advice. In others, NJU conducted
essentially the entire evaluation.
The goal of the project was to encourage participation in the
assessment process by management and staff at the facility. To do
this, the participants were encouraged to proceed through the
organizational steps outlined in the manual. These steps can be
summarized as folbws:
• Obtaining corporate commitment to a waste minimization
initiative
• Organizing a task force or similar group to carry out the
assessment
• Developing a policy statement regarding waste minimiza-
tion for issuance by corporate management
• Establishing tentative waste reduction goals to be achieved
by the program
• Identifying waste-generating sites and processes
• Conducting a detailed site inspection
• Developing a list of options which may lead to the waste
reduction goal
• Formally analyzing the feasibility of the various options
• Measuring the effectiveness of the options and continuing
the assessment.
Not every facility was able to follow these steps as presented. In
each case, however, the identification of waste-generating sites and
processes, detailed site inspections, and-development of options
was carried out. Frequently, it was necessary for a high degree of
involvement by NJIT to accomplish these steps. Two common
reasons for needing outside participation were a shortage of techni-
cal staff within the company and a need to develop an agenda for
technical action before corporate commitment and policy statements
could be obtained.
It was not a goal of the ARROW project to participate in the
feasibility analysis or implementation steps. However, NJIT offered
to provide advice for feasibility analysis if requested.
In each case, the NJIT team made several site visits to the facility.
Initially, visits were made to explain the EPA manual and to encourage
the facility through the organizational stages. If delays and compli-
cations developed, the team offered assistance in the technical
review, inspections, and option development
No sampling or laboratory analysis was undertaken as part of these
assessments.
Facility Background
The facility purchases scrap metal from manufacturers in the United
States and throughout the world and uses recovery technology to
produce marketable quantities and quality of tungsten, molybdenum,
and tantalum. The facility uses techniques of cleaning and acid
treatment to recover and prepare the metals for resale.
The facility is located in a suburban area and employs about 25
people. This particular facility is one of the few businesses of its type
in operation in the world. This assessment presents an interesting
opportunity to consider what happens to materials from pollution
preventbn activities at other types of facilities which are sent offsite
for recovery.
Manufacturing Processes
The metal recovery processes used at the facility are different for the
three major types of metals which form the core of the activity.
Tungsten scrap is simply washed with nitric acid to remove impuri-
ties. Molybdenum scrap is washed with commercial detergents in
water to remove grease and cutting oils. The degreased surfaces
are cleaned further using mechanical means such as sand-blasting.
The tantalum is recovered most frequently by extraction from ca-
pacitors which have plastic resin components as well. The capacitors
are crushed and the plastic is separated by a water wash taking
advantage of the differential in the density of the two materials. The
recovered tantalum is treated with nitric acid and with hydrochloric
acid to remove contaminants.
Existing Waste Management Activities
The company represents an important part of the pollution prevention
infrastructure. The processes and procedures earned out at this
facility demonstrate that recovery from waste streams of materials
for reuse is an industrial process and also has potential for pollution
preventbn activities. This facility has already considered opportunities
for pollutbn preventbn. For example, degreasing of the molybdenum
scrap is carried out with aqueous detergents rather than with solvents
and the removed grease and cutting oils are separated from the
water and sent for recovery. Further cleaning of the molybdenum
scrap is done mechanically, rather than chemically. The goal of this
assessment was to identify additbnal opportunities for pollutbn
preventbn at the facility.
Because the processes for the recovery of the three major metals of
interest are different, they produce somewhat different types of
waste streams. For the tungsten process, the scrap is treated with
70% nitric acid and then rinsed. The acid washes and the rinses are
sent to a common sump for further processing.
The molybdenum scrap is washed with aqueous detergents to
remove grease and oil. The oil layers are separated mechanically
and sent offsite for heat value recovery. The aqueous layer is sent to
the POTW. Further cleaning of the metal is done by sand-blasting
whbh results in productbn of nonhazardous solid waste.
Recovery of tantalum requires separatbn of the metal from the
plastb components of capacitors. This separatbn is accomplished
by mechanical crushing and then washing away the plastb compo-
nents with water. The recovered metal is cleaned by treatment with
hot concentrated nitric acid, folbwed by a second wash with hydro-
chbric acid. The metal is then rinsed with water. All of the acid
washes and the rinses are sent to the same common sump used for
the tungsten recovery process.
The liquid in the sump is processed periodically by pH adjustment
with caustic folbwed by additbn of ferric chbride to act as a
coagulant. The mixture is then passed through a filter press to
recover solids. The effluent is passed through a bag filter for
polishing and then is sent to a holding tank for a final pH check and
adjustment, if necessary. After an additbnal pass through a bag filter
for polishing the effluent is discharged to the POTW. The solids from
the bag filters are returned to the filter press.
The facility produces about 8-9,000 Ib/month of nonhazardous solids
from the filter press whbh are sent offsite for disposal. About 900 gal
of effluent is discharged to the POTW daily. Some concerns about
the effluent include occasbnally exceeding the albwable tungsten
limit, occasbnal elevated levels of phenols, and total dissolved
solids whbh exceed the standards of the POTW.
Waste Minimization Opportunities
The type of waste currently generated by the facility, the source of
the waste, the quantity of the waste and the annual treatment dnd
disposal costs are given in Table 1.
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Table 2 shows the opportunities for waste minimization recom-
mended for the facility. The type of waste, the minimization
opportunity, the possible waste reduction and associated sav-
ings, and the implementation cost along with the payback time
are given in the table. The quantities of waste currently gener-
ated at the facility and possible waste reduction depend on the
level of activity of the facility.
It should be noted that the economic savings of the minimiza-
tion opportunity, in most cases, results from the need for less
raw material and from reduced present and future costs asso-
ciated with waste treatment and disposal. It should also be
noted that the savings given for each opportunity reflect the
savings achievable when implementing each waste minimization
opportunity independently and do not reflect duplication of
savings that would result when the opportunities are imple-
mented in a package. Also, no equipment depreciation is
factored into the calculations.
Some of the major issues to be addressed include reduction of
the level of dissolved solids in the aqueous effluent, lowering of
the tungsten level in the effluent, and addressing the issue of
phenols in the effluent.
Total dissolved solids can come from many sources. This
facility uses substantial quantities of concentrated acid which is
neutralized with caustic. The neutralization results in salt for-
mation. Additionally, coagulation of suspended solids is ac-
complished with ferric chloride, which can also result in pro-
duction of additional dissolved solids after neutralization. It is
also true that the acids are used largely for the purpose of
dissolving material from the scrap metal. The dissolved materi-
als that are not precipitated when the solution is neutralized
are carried along in the effluent.
A potential solution to this problem may be to extend the life of
the acid baths. The current practice is to visually examine the
baths after treatment of each batch of metal. If the acid in the
bath is discolored or appears to be contaminated, it is discarded
into the neutralization tank. Otherwise, it is returned to the
process. The management estimates that about 20% of the
nitric acid is recycled. It would appear that a more analytical
approach to evaluate the continued effectiveness of the acid
would allow more of it to be recycled. Because the process
depends upon acid mediated reaction of the surface of the
* Mention of trade names or commercial products does not constitute endorsement
or recommendation for use.
metal fragments, the process could continue even if the acid is
discolored as long as the pH is sufficient for reaction with the
metal. It may be more effective to determine the optimum
range of pH for the surface cleaning to occur and to continue
using the acid bath as long as the pH remains in that range.
The life time of the bath conceivably could be extended further
by mixing of addition of fresh acid. Ultimately, it may be
desirable to consider uses for this acid stream other than
straight neutralization and discharge to the POTW. It could be
collected and sent for treatment as hazardous waste. Alterna-
tively, and better from a pollution prevention perspective, it
could be listed on a waste exchange and offered for use in the
processes of other organizations.
The issue of phenols in the aqueous effluent appears to be
related to the plastic materials which are separated from the
tantalum metal contained in capacitors. Current practice is that
once the capacitors are crushed, the plastic material is washed
away with water and the washings are transferred directly to
the common sump. Assuming that the plastic is a phenolic
based resin, it would be common for a depolymerization to
take place under acid conditions, resulting in elevated levels of
free phenols. It is recommended therefore that this stream be
segregated and that it be handled through the filter press
separately. In any event, it is desirable to avoid exposure of
this material to acid conditions.
Regulatory Implications
A significant incentive for consideration of additional pollution
prevention opportunities at this facility was the level of certain
materials in the wastewater discharged to the POTW for treat-
ment. This concern was the result of clean water regulations. If
decisions are made to segregate acid streams and to send
them offsite for treatment, then the facility will become a haz-
ardous waste generator and a new type of regulatory scrutiny
will come into place.
This Research Brief summarizes a part of the work done under
cooperative Agreement No. CR-815165 by the New Jersey
Institute of Technology under the sponsorship of the New
Jersey Department of Environmental Protection and Energy
and the U.S. Environmental Protection Agency. The EPA Project
Officer was Mary Ann Curran. She can be reached at:
Pollution Prevention Research Branch
Risk Reduction Engineering Laboratory
U.S. Environmental Protection Agency
Cincinnati, OH 45268
Table 1. Summary of Current Waste Generation
Waste Generated Source of Waste
Nonhazardous Solid
Waste
Aqueous Discharge to
POTW
Solids recovered from aqueous
stream through filter press
Neutralized acid stream, rinses,
and plastic residue washings
after passing through the
filter press
Annual Quantity
Generated
102,000 Ib
225,000 gal
Annual Waste
Management Costs
$3600
400
(In addition to these direct charges,
processing charges for chemicals and
equipment add an estimated $10,000
annually to these costs.)
•(fV.S. GOVERNMENT PRINTING OFFICE: 1994 - 550-067/8017H
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Table 2. Summary of Recommended Waste Minimization Opportunities
Waste Stream
Reduced
Phenolics in Effluent
Dissolved Solids
in Effluent and
Filter Press Cake
Tungsten Level in
Aqueous Effluent
Acid Streams
Minimization Opportunity
Annual Waste Reduction
Quantity
Percent
Net Implementation Payback
Annual Savings Cost Years *
Segregate capacitor plastic
residues from exposure
to acid conditions to minimize
polymer degradation and phenol
formation
Investigate use of organic
polymer as coagulant in place
of ferric chloride. This should
reduce the levels of dissolved
solids in the discharge and reduce
the quantity of the filter cake.
Segregate tungsten processing
stream, neutralize with calibrated
pH measuring equipment to assure
reproducible endpoint. Segregation
will eliminate the possibility of
formation of a soluble complex of
tungsten and components of other
processing stream
Extend lifetime of acid baths
by developing quantitative methods
to determine when they are no longer
effective. The methods could include
pH measurements, dissolved solids
content, water content, or other variables.
A realistic initial goal would be for 50%
reuse rather than the present 20%.
(There would be essentially no change in waste quantity, rather the
quality of the waste stream would be improved by lowering the level
ofphenolics in the effluent improving the ability of the POTW to
manage the effluent.)
20,400 Ib
20
$720
1.7
(There would be essentially no change in waste quantity, rather the
quality of the waste stream would be improved by lowering the level
of tungsten in the effluent, improving the ability of the POTW to
manage the effluent.)
38,250 Ib
37.5
5,350
3,000
0.6
* Savings result from reduced raw material and treatment and disposal costs when implementing each minimization opportunity independently.
United States
Environmental Protection Agency
Center for Environmental Research Information
Cincinnati, OH 45268
Official Business
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