United States

domestic arsenic wastes would be converted to a
useable commodity. This, however, would adversely
affect importers and may be politically undesirable as

a restraint of international trade. Also, domestic -

production may be unable to satisfy demand.

Further development work should be conducted on
molten sulfur, cements, and materials containing
sulfhydryl groups. Sulfur and cements simply require
optimization of waste loadings and conducting more
leaching tests. Using sulfhydryl groups requires
selecting materials, optimizing waste loadings, and
probably selecting an encapsulation system (e.g.,
cement). These generic processes may not yield
improvements in leaching resistance over
commercial processes, but they may yield savings in
cost or provide methods that can be directly used by
waste generators.

This Research Brief describes work done under
Contract No. 68-03-2503 by JBF Corporation under
the sponsorship of the U.S. Environmental Protection
Agency.

Donald E. Sanning, the EPA Project Officer, is with
the Municipal Environmental Research Laboratory,
Cincinnati, OH 45268.

Environmental Protection Information

Agency

Cincinnati OH 45268

Center for Environmental Research

Postage and
Fees Paid
Environmental
Protection
Agency

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Official Business
Penalty for Private Use $300


United States
Environmental Protection
Agency

Municipal Environmental Research
Laboratory
Cincinnati OH 45268

Research and Development EPA-600/D-81-104 August 1982

ENVIRONMENTAL
RESEARCH BRIEF

EPA

Stabilization, Testing, and Disposal of

Arsenic Containing Wastes

Jaret C. Johnson and
JBF Scientific Corporation,

Commercially available treatment processes
intended to reduce leaching of contaminants from
wastes were evaluated for arsenic-laden industrial
wastes. Three wastes were selected: (1) residues
from the production of arsenical herbicides, (2) filter
cake from the refinement of food-grade phosphoric
acid, and (3) flue. dusts from nonferrous metal
smelters. Each of these wastes was treated with
many treatment (fixation) processes. The processes’
ability to retard the leaching of arsenic was evaluated
through the results of laboratory leaching tests.
Several processes reduced arsenic leaching rates by
at least four orders of magnitude. Other processes
were much less effective.

Introduction

Arsenic is present in many industrial solid wastes,
and improper disposal of some of these wastes has
caused contamination of some groundwaters. More
properly managed arsenic-bearing wastes have often
been kept in dry storage, which is only a temporary
option. The need for improved methods for managing
arsenic-bearing wastes was the stimulus for this
work,

The passage of the Resource Conservation and
Recovery Act of 1976 (RCRA, PL 94-580) also added
importance to this work. Rules for implementing this
law have recently been promulgated, and the rule-
making process is continuing to resolve issues left
uncertain by those rules. In particular, the develop-

Robert L. Lancione
Wilmington, MA 01887

ment of rules for Section 3001 of RCRA (identification
and listing of hazardous waste) prompted some of the
work in this project.

Purpose and Scope

This study was done to develop recommendations,
based on laboratory test data, for the environmentally
safe disposal of arsenic-bearing wastes. The labora-
tory tests were to evaluate the fixation processes’
ability to retard the leaching of arsenic. The major
efforts were to:

1. Identify the arsenic-bearing wastes of greatest

environmental significance.

Identify new and available fixation technologies.
Both commercially available processes and
generic methods that might be performed with
ease and economy by waste generators were
evaluated. This effort was carefully coordinated
with experimental work on arsenic-laden flue
dusts being conducted at the Montana Tech
Foundation Mineral Research Center so that
duplication would be avoided.

Test the effectiveness of fixation processes.
Four tests were performed assessing several
aspects of leaching potential.

Evaluate the potential for increased commercial
use of arsenic and its compounds to reduce
amounts requiring disposal.

DS» Ss»


Definitions and Identifications

The terms fixation, immobilization, and stabilization
are used interchangeably throughout this report for
the processes applied to the wastes.

Publicity or endorsement of any specific commercial
processes was not the purpose of this work. The goal
was determining whether any commercial processes
effectively reduced arsenic leaching from each waste
and to what extent. In this way, EPAcan use the work
to assess the state of the art and to help develop
regulations. Therefore, leaching test results for
commercial products identified the processors by
code letters in all project reports.

Generation and Potential Use of Wastes

The principal domestic sources of industrial wastes
that contain arsenic are nonferrous metal smelters,
chemical process industries producing food-grade
phosphoric acid (by removing arsenic from the
product), pesticide manufacturers, and veterinary
pharmaceuticals producers. Of these sources, only
the nonferrous metal smelters produce arsenic as a
commodity.

We also acquire a supply of arsenic through importa-
tion. Although annual figures of supply of, and
demand for, arsenic and its compounds are very
erratic, some generalizations can be made. During
the 1970's, approximate typical annual figures were
(all data in metric tons of arsenic):

Imports 9,000

Domestic Production 19,000
(Including net

transfers to/from

storage)

TOTAL SUPPLY 28,000

TOTAL DEMAND 19,000

These figures show that the excess of supply over
demand is approximately equal to the amount of
arsenic imported. If imports were banned, however,
the arsenic disposal problem would not necessarily
be eliminated.

The, primary users of arsenic have an uncertain
future. Arsenic-containing pesticide manufacturers,
the major users, are under constant regulatory
pressure regarding workplace exposure to arsenic as
well as maintaining registrations (EPA approval for

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specific uses of the product). Other users are also
uncertain, primarily because of workplace exposure
regulations. These users include the glass industry
and wood preservative manufacture and those using
arsenic as an alloying element in metals or as a
component of semiconductors and photovoltaic cells.

Three types of arsenic-laden wastes are particularly
important: The volume and arsenic concentration of
flue dusts from the primary nonferrous smelting
industry, filter cake from the purification of food-
grade phosphoric acid, and salt residues from the
manufacture of organic arsenical herbicides. These
byproducts of industrial activities vary in the chemical
form of arsenic and in the physical-chemical proper-
ties of the bulk matrix. Testing of these wastes
therefore provided a range of challenges to the
fixation processes.

Effectiveness of Fixation Processes

Fourteen proprietary processes and nine generic
processes were applied to the three types of wastes; a
few of the waste/process combinations were incom-
patible. Most effort was given to vendor processing
rather than developing generic processes. Three
factors guided this approach: (1) The broad range of
concepts used by commercial or academic process
developers. (2) Development of new approaches is
time-consuming and involves the risk of being unsuc-
cessful. (3) Vendors furnished approximate cost
estimates that appeared not to be prohibitively high,
so the economic need to develop ‘do-it-yourself’
processes for waste generators was not great.

Four kinds of leaching tests were applied to each
treated waste. For control and reference, each waste
without treatment and each fixation process reagent
mix without waste was subjected to the same leach-
ing test. These leaching tests demonstrated the
existence of several processes, both proprietary and
generic, that can significantly reduce the amount of
arsenic release and the rate of release relative to
untreated wastes. Also ‘demonstrated was the
importance of the type of leaching test on the results.

Shake Tests

During the shake test, each material was immersed in
distilled water, with gentle agitation to prevent fluid
stratification. Every 2 days the water was changed,
with an aliquot taken for analysis. Leaching behavior
was thus assessed over a period of up to 2 months for
each sample. Each test was duplicated, and analytical
quality control was achieved through internal checks
and more than 200 blind replicate comparisons with
an outside laboratory.


These tests show commercially available fixation
processes offer a wide range of effectiveness in
reducing the leaching of arsenic from the three
wastes. Some processes reduced leaching rates by
more than four orders of magnitude relative to raw
wastes, and some were less effective. Processes also
vary in their behavior with time: leaching rates for
some waste/process combinations increased with
time whereas others decreased. Detailed results of
the shake tests are provided in a paper prepared for
submittal to a peer-review journal.

Brief Elutriate Tests on Crushed Samples

A violent 24-hour shake test with crushed samples
was performed in distilled water. In this test, breaking
the monolithic structures was intended to simulate
physical breakdown in the field.

The samples of treated pesticide manufacturing
waste all released much of their arsenic; the percent
leached from both proprietary and generic samples
ranged from 28% to 100%. Arsenic leaching from
treated samples of other wastes was much lower and
more variable from process to process. These test

results, viewed as process effectiveness, were quite ©

different from the shake test results on intact
samples. The two tests therefore can be used to
provide information about fundamentally different
aspects of leaching behavior.

Elutriate tests on samples fixed by generic (nonpro-
prietary) methods in the laboratory suggested that
molten sulfur, cements, and materials containing
sulfhydryl groups have promise as relatively easy-to-
use fixing agents.

Extraction Procedure

This work was conducted while EPA was developing
methods to identify hazardous wastes under Section
3001 of RCRA. An early version of the extraction
procedure (EP) was used in this project in support of
EPA's rulemaking. The version used here called for
sample crushing, 48-hour exposure to water, main-
tenance of pH near 5.0, and moderate agitation.
Results were generally similar to those from the
élutriate test. Some samples, however, were
adversely affected by the pH control in the EP. Cement
matrices, for example, maintain some arsenic forms
as\insoluble primarily because of the matrices’
alkalinity. This effect is nullified by the acid additions
in the EP.

Shake Kest With Landfill Leachates

The shake tests were repeated. This time two real
landfill leachates collected from municipal landfills in

'# US. GOVERNMENT PRINTING OFFICE: 1982-559-017/0777

Enfield (Connecticut) and Barre (Massachusetts),
rather than distilled water, were used. Data were of
limited applicability because attempts to avoid
chemical precipitation in the water samples after
filtration were not completely successful. A negative
bias resulted in the data for arsenic leaching.

Recommendations

The following recommendations are presented in
order of priority:

The present form of the EP should be applied to the
more promising waste/product combinations
evaluated in this project. This test now allows use of
monolithic structures that survive a compaction test.

Field lysimeter tests should be conducted on fixed
arsenic-laden wastes to confirm and extend the find-
ings of this laboratory study. Stresses such as
freeze/thaw, wet/dry, and hot/cold cycles can thus
be assessed. Co-disposal with municipal solid waste
can also be assessed under field conditions in this
manner. Without such field data, EPA cannot
adequately judge the full-scale use of the waste/
process combinations assessed in this laboratory
study.

A protocol should be designed and used that
eliminates the problem of chemical precipitation in
shake tests with landfill leachates. Other studies
have investigated pollutant attenuation with oxygen-
free test conditions, as well as analytical methods for
leachates. Some of the techniques used in those
studies may be adaptable to the development of a
shake test/sample processing/sample analysis
protocol that accurately simulates anoxic conditions
in a landfill. For example, shake testing, filtration, and
sample storage might be done in glove bags with a
nitrogen or CO2 atmosphere.

A study should be made of the effect of the OSHA
standard for arsenic exposure in the workplace on the
generation of unmarketable arsenic-laden flue dusts.
Predictions reviewed in this study suggest that
markets for arsenic derived from these dusts will
decline because of industries’ cost to achieve the
OSHA standard and because of some industries’
discontinued use of arsenic. Actual developments
should be followed, not only for EPA to keep abreast of
the problems with arsenic-laden wastes, but also to
gain general insight into secondary effects of one
agency's actions (e.g., OSHA) on other agencies’
responsibilities (e.g., EPA).

The economic and environmental implications of
arsenic imports should be assessed. Limiting imports
could lessen disposal problems because more

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