1
Peer
Review
Comments
on:

Technical
Background
Document:
Mercury
Wastes
Evaluation
of
Treatment
of
Mercury
Surrogate
Waste
January
24,
2003
Submitted
by:

Science
Applications
International
Corporation
Engineering
and
Environmental
Management
Group
11251
Roger
Bacon
Drive
Reston,
Virginia
20190
Submitted
to:

U.
S.
Environmental
Protection
Agency
Ariel
Rios
Building
Office
of
Solid
Waste
1200
Pennsylvania
Avenue,
N.
W.
Washington,
D.
C.
20460
EPA
Contract
No.
68­
W0­
0122
Work
Assignment
No.
1­
2
SAIC
Project
No.
06­
0758­
08­
2889­
000
2
Evaluation
of
Treatment
of
Mercury
Surrogate
Waste
In
order
to
help
evaluate
whether
EPA
could
propose
treatment
and
disposal
alternatives
to
the
current
land
disposal
restriction
(
LDR)
treatment
standard
of
mercury
retorting,
EPA
conducted
a
study
on
the
treatment
of
a
surrogate
waste
contaminated
with
multiple
forms
of
mercury.
The
study
was
performed
to
assess
conditions
that
affect
the
stability
of
waste
residues
resulting
from
the
treatment
of
high
mercury
(
greater
than
260
mg/
kg
total
mercury)
wastes.
The
results
of
the
study
were
submitted
for
formal,
independent
peer
review
by
three
national
experts
with
significant
technical
expertise
in
hazardous
waste
leaching.
These
peer
reviewers
have
no
prior
association
with
this
study,
and
have
no
perceived
or
actual
conflict
with
any
impact
of
the
study
results.
The
members
of
the
peer
review
panel
were
tasked
with
evaluating
the
adequacy
of
the
experimental
design,
conduct,
and
conclusions
of
the
study.
The
peer
review
panel
also
provided
information
on
how
the
study
can
be
used
to
provide
a
framework
to
determine
whether
additional
protective
measures
are
required
to
prevent
loss
of
mercury
to
the
environment
from
the
treatment
and
co­
disposal
of
mercury­
bearing
wastes
in
landfills.
Additionally,
the
members
of
the
peer
review
panel
were
asked
if
additional
studies
were
warranted
for
other
factors
that
impact
solubility
(
e.
g.,
liquid/
solid
ratio,
redox
conditions,
leachate
composition)
or
affect
ability
to
leach
(
such
as
use
of
macroencapsulation).
The
specific
questions
asked
of
the
peer
reviewers
are
provided
in
this
document,
along
with
the
peer
reviewer's
comments,
and
EPA's
responses
to
those
comments.

Charge
Question
1:
Was
the
experimental
design
of
the
study
appropriate?

Reviewer
#
1:
Yes.
My
review
of
the
report
and
the
accompanying
appendices
indicates
that
this
study
was
conducted
with
clearly
defined
objectives
and
with
careful
designing
and
implementation
of
the
testing
details.
This
study
was
a
controlled
laboratory
study
that
focused
on
creating
a
surrogate
waste
sludge
covering
multiple
forms
of
mercury
at
high
concentrations.
This
study
focused
on
laboratory
leaching
tests
to
determine
the
effectiveness
of
treatment
technologies
that
were
tested.
Sufficient
replicates
were
utilized
and
a
number
of
technologies
were
selected
and
tested
in
the
study
in
an
appropriate
manner.

Reviewer
#
2:
The
design
did
not
follow
the
Data
Quality
Objectives
process,
nor
a
similar
planning
process.
As
a
result,
there
is
little
relationship
between
the
objectives
and
the
design.
A
RCRA
disposal
scenario
was
implied,
but
the
pH
range
did
not
extend
to
pH
12.5,
and
data
show,
e.
g.,
Figure
5.3,
that
major
changes
occur
in
extraction
at
high
pH.

Response:
EPA
has
developed
the
DQOs
process
as
the
Agency's
recommended
planning
process
when
environmental
data
are
used
to
select
between
two
opposing
conditions,
such
as
achieving
or
not
achieving
a
numerical
standard.
The
DQOs
process
is
used
to
develop
qualitative
and
quantitative
statements
of
the
overall
level
of
uncertainty
that
a
decision­
maker
is
willing
to
accept
in
results
or
decisions
derived
from
environmental
data,
i.
e.,
Data
Quality
Objectives.
The
DQOs
process
entails
a
seven
step
systematic
procedure
for
defining
the
criteria
that
a
data
collection
design
should
satisfy,
including
when
to
collect
samples,
where
to
collect
3
samples,
the
tolerable
level
of
decision
error
for
the
study,
and
how
many
samples
to
collect,
balancing
risk
and
cost
in
an
acceptable
manner.
When
this
process
is
not
directly
applicable
(
i.
e.,
the
experimental
objective
is
estimation,
research,
or
any
other
objective
that
does
not
select
between
two
distinct
conditions),
the
Agency
recommends
the
use
of
a
systematic
planning
method
for
defining
performance
criteria.
For
this
research
project,
a
systematic
planning
method
was
used.
A
Quality
Assurance
Project
Plan
(
QAPP)
was
developed
by
EPA
and
was
followed
throughout
the
project.
EPA
believes
that
the
project
objectives
and
criteria
were
logical,
given
the
intended
end­
use
of
the
data,
well­
defined,
and
achievable.

The
reviewer
has
placed
undue
significance
on
pH
12.5.
Few
Landfills
exhibit
such
extreme
conditions.
We
believe
the
trend
of
performance
can
be
adequately
established
with
testing
in
the
pH
2
­
12
range.
However,
if
disposal
under
extreme
conditions
were
planned,
then
we
concur
that
testing
should
encompass
such
conditions
with
testing
at
pH
13
or
above.

The
QAPP
for
this
study
was
also
included
in
the
electronic
file
for
the
evaluation
of
bulk
elemental
mercury.
A
statement
of
accreditation
for
the
labs
could
have
been
substituted
for
much
of
the
generic
material
in
the
QAPP.

Response:
The
QAPP
approved
for
this
study
was
developed
according
to
EPA
QA
R­
5
guidelines.

Reviewer
#
3:
The
experimental
design
employed
was
appropriate
in
most
regards.
One
problem
with
the
plan
was
the
variability
introduced
by
having
vendors
prepare
the
surrogate
waste.

Response:
EPA
provided
each
of
the
vendors
with
all
of
the
components
necessary
to
prepare
the
waste,
with
the
exception
of
water,
and
instructions
for
combining
the
materials,
including
how
much
water
to
add.
This
approach
was
chosen
because
it
was
faster
and
cheaper
to
ship
the
individual
components
to
the
vendors
rather
than
to
ship
the
prepared
surrogate
waste.
EPA
had
anticipated
that
the
participants
would
follow
the
preparation
directions
closely.
This
was
not
the
case.
In
retrospect,
EPA
would
not
use
this
approach
again.

Data
in
Appendix
C
shows
that
concentrations
of
potassium,
calcium
and
magnesium
were
much
higher
in
the
surrogates
prepared
by
all
vendors
than
the
surrogate
prepared
by
Alter.
Furthermore,
the
concentrations
of
chloride
in
surrogate
waste
prepared
by
Vendors
A,
B,
and
C
were
much
higher
than
concentrations
in
the
surrogate
prepared
by
Alter
and
Vendor
D.
Chloride
concentrations
are
particularly
important
because
of
the
ability
of
chloride
ions
to
form
soluble
complexes
with
mercury,
thereby
enhancing
its
release
during
leaching
tests.
Therefore,
it
is
possible
that
the
surrogate
waste
treated
by
Vendor
D
was
"
easier"
to
treat,
than
that
treated
by
the
other
vendors.
Vendor
C
reported
using
only
about
one
half
of
the
specified
water
in
preparing
its
surrogate
waste.
The
effect
of
reduced
water
content
in
the
surrogate
waste
on
performance
in
leaching
tests
is
not
clear,
but
the
lack
of
consistency
in
surrogate
waste
preparation
is
undesirable.
4
Response:
EPA
does
not
believe
that
the
variability
of
the
surrogate
waste
is
as
large
as
implied
by
the
reviewer.
The
measured
concentrations
of
potassium
and
chloride
in
the
untreated
surrogate
prepared
by
Alter,
Inc.
and
the
four
vendors
are
all
within
1
order
of
magnitude
of
each
other.
The
concentration
of
calcium
is
very
similar
in
the
wastes
prepared
by
all
four
vendors.
With
one
exception
(
Vendor
C),
the
concentration
of
magnesium
in
the
waste
prepared
by
Alter
and
the
vendors
varies
within
one
order
of
magnitude.
We
believe
that
this
variation
does
not
adversely
impact
the
results
of
the
study,
nor
the
conclusions
based
on
those
results.

Charge
Question
2:
Was
the
study
conducted
properly?

Reviewer
#
1:
Yes.
My
review
of
the
SAIC
(
2000)
report
indicates
that
all
vendors
and
laboratories
properly
carried
out
the
surrogate
sample
preparation,
and
the
leaching
tests
on
the
prepared
treated
surrogate
waste
samples.
All
characterization
data
appears
to
be
properly
collected
and
reported.

Reviewer
#
2:
The
appropriate
procedures
were
used,
and
the
study
appears
to
have
been
done
as
planned.

Reviewer
#
3:
The
conduct
of
the
study
appears
to
have
been
proper.

Charge
Question
3:
Were
the
stated
objectives
adequately
met?

Reviewer
#
1:
Yes,
for
the
most
part.
The
study
objectives
as
stated
in
the
report
dealt
with
(
1)
an
evaluation
of
alternative
stabilization
process
by
examining
the
TCLP
test
results
to
meet
a
goal
of
0.025
mg/
L
or
less,
and
(
2)
to
compare
proposed
new
leaching
test
protocols
to
the
standard
TCLP
results.
The
study
also
included
leach
testing
of
pellets
and
crushed
forms
of
the
stabilized
wastes.
Fixed
pH
leach
tests
were
replicated
only
part
of
the
time.
The
results
and
graphs
presented
in
the
report
clearly
indicate
that
leachate
concentrations
derived
from
the
stabilized
waste
are
always
significantly
lower
than
those
obtained
from
the
un­
stabilized
waste.
The
results
presented
also
show
that
there
are
significant
differences
in
the
effectiveness
of
the
various
treatment
technologies
that
were
tested.
The
results
further
show
that
the
constant
pH
leaching
test
results
depict
a
pH
dependent
leaching
behavior
of
mercury.
Based
on
this
one
surrogate
waste
testing
results,
it
also
appears
that
Vendor
A
technology
performs
the
best
except
when
the
stabilized
waste
is
exposed
to
very
alkaline
condition
(
i.
e.,
pH
>
11.0).
Vendor
B
stabilized
waste
seems
to
meet
the
0.025
mg/
L
goal
only
for
the
very
alkaline
condition,
and
Vendor
C
stabilized
waste
meets
the
leachate
goal
of
0.025
at
pH
greater
than
9.
The
Vendor
D
stabilized
waste
meets
the
0.025
mg/
L
goal
only
at
pH
greater
than
10.

Therefore,
this
report
should
conclude
that
all
treatment
technologies
that
were
tested
are
not
equally
effective,
and
that
Vendor
A
technology
provides
the
most
treatment
effectiveness
for
a
much
broader
range
of
pH
conditions
than
the
other
three
vendors.
This
report
should
also
recognize
that
the
new
leaching
test
protocols
yield
significantly
different
results
than
TCLP
test.
5
This
is
not
surprising
in
light
of
the
fact
that
TCLP
test
was
developed
to
simulate
a
mismanagement
case
of
waste
disposal
in
a
municipal
landfill,
whereas
the
constant
pH­
leaching
test
covers
a
broad
range
of
environmental
conditions
for
leaching.

Response:
The
intent
of
this
study
was
to
evaluate
the
stability
of
treatment
residuals
from
commercially
available
technologies
against
bench
mark
standards,
and
not
to
compare
the
technologies
to
each
other.
Therefore,
EPA
believes
that
it
is
inappropriate
to
reach
the
relative
conclusions
suggested
by
the
reviewer.
The
testing
protocol
of
the
TCLP
yields
final
pH
conditions
that
differ
for
each
waste
tested.
However,
the
concentrations
measured
were
consistent
with
the
concentration
gradients
indicated
by
the
constant
pH
protocol
measurements.
In
general,
the
two
test
procedures
provide
similar
results
when
compared
at
the
same
pH
level.
In
some
cases,
TCLP
results
are
lower.
This
could
be
due
to
equilibrium
not
being
attained
in
the
shorter
exposure
period
of
the
TCLP.

A
couple
of
editorial
suggestions
are
added
here
for
the
summary
tables
in
the
report.
Tables
containing
analytical
results
on
TCLP
for
the
various
vendors
(
e.
g.,
Table
5­
3)
should
be
better
labeled
to
show
which
are
pelletized
samples,
which
are
crushed
samples,
and
which
ones
are
untreated
samples.

Response:
These
editorial
suggestions
were
implemented
in
a
final
revision
of
the
study
report.

Reviewer
#
2:
The
first
objective
in
the
peer
review
charge
was
to
evaluate
alternative
treatment
technologies
to
obtain
a
goal
of
0.025
mg/
L
Hg
over
a
range
of
pH
2
to
pH
12.
This
objective
was
adequately
met
with
the
exception
of
an
apparent
sample
heterogeneity
problem.

Response:
EPA
agrees
that
sample
heterogeneity
was
a
recurring
issue,
albeit
a
minor
one.
We
believe
that
the
sample
heterogeneity
is
inherent
in
the
nature
of
both
the
untreated
and
treated
materials,
and
difficult
to
control.
As
the
study
was
intended
to
evaluate
the
treatment
residuals
from
the
stabilization
technologies
as
they
are
used
commercially,
we
believe
that
this
heterogeneity
is
a
variable
that
must
be
considered.

The
second
objective
was
to
compare
constant
pH
protocol
results
to
standard
TCLP
results.
This
was
adequate
with
the
exception
of
the
apparent
sample
heterogeneity.

Response:
As
noted
in
the
previous
response,
EPA
agrees
that
sample
heterogeneity
was
a
minor,
recurring
issue.
We
believe
that
it
is
useful
to
compare
the
constant
pH
leaching
protocol
to
the
TCLP,
and
that
any
minor
issues
caused
by
heterogeneity
do
not
interfere
with
that
comparison.

Reviewer
#
3:
a)
Effectiveness
of
meeting
goal
of
0.025
mg/
L
in
leaching
tests
i)
TCLP
Test
The
treatment
process
of
Vendor
A
was
able
to
consistently
meet
the
goal
(
0.025
mg/
L)
in
the
6
TCLP
test
by
substantial
margin
(
concentrations
<
0.01
mg/
L).
There
was
little,
if
any,
difference
between
the
treated
materials
in
crushed
or
pellet
forms.
The
ability
of
this
treated
waste
to
meet
the
goal
was
confirmed
by
its
performance
in
the
constant
pH
leaching
test
(
CPLT),
in
which
concentrations
were
measured
below
the
goal
at
pH
values
near
that
observed
in
the
TCLP.

The
treatment
process
of
Vendor
B
was
not
able
to
meet
the
goal
in
any
samples
submitted.
This
performance
was
confirmed
by
the
CPLT.

The
treatment
process
of
Vendor
C
was
able
to
meet
the
treatment
goal
in
all
samples
submitted
(
Batch
1,
Batch
2).
The
degree
by
which
the
goal
was
exceeded
was
greater
in
Batch
2
than
Batch
1.
This
behavior
was
confirmed
by
performance
in
the
CPLT,
although
concentrations
were
higher
in
the
CPLT.

The
treatment
process
of
Vendor
D
was
able
to
meet
the
treatment
goal
in
one
sample
submitted
(
Batch
1),
but
did
not
meet
the
treatment
goal
in
another
sample
(
Batch
2).
The
average
TCLP
concentration
for
Batch
2
exceeded
the
goal,
although
one
sub­
sample
out
of
three
was
lower
than
the
treatment
goal.
This
performance
was
confirmed
by
performance
of
Batch
#
2
in
the
CPLT.
However,
Batch
#
1
gave
a
very
high
concentration
in
the
CPLT
near
the
pH
of
the
TCLP.
However,
this
point
does
not
follow
the
general
trend
of
the
rest
of
the
data
for
this
treated
waste
or
the
treated
wastes
of
other
vendors,
so
it
appears
to
be
an
outlier.

These
results
support
the
conclusion
that
there
are
existing
stabilization
technologies
that
can
meet
a
TCLP
goal
of
0.025
mg/
L
in
wastes
with
mercury
concentrations
well
in
excess
of
260
mg/
kg.

ii)
Constant
pH
test
Only
a
few
(
pH
2,
8,
12)
CPLT
were
replicated,
so
there
is
limited
data
to
evaluate
the
reproducibility
of
the
test
procedure.
The
average
relative
percentage
difference
(
RPD)
for
all
vendors
was
35%,
but
many
individual
RPD
exceeded
100%.
This
limits
the
confidence
that
can
be
placed
on
individual
test
results,
especially
when
they
approach
the
treatment
goal.

Response:
The
number
of
test
replicates
that
could
be
conducted,
and
consequently
the
amount
of
data
that
could
be
collected,
was
limited
by
available
resources.
EPA
believes
that
sufficient
data
are
available
to
consider
the
data
set
in
aggregate,
and
to
support
the
conclusions
presented
in
the
report.

The
treatment
process
of
Vendor
A
was
able
to
meet
the
treatment
goal
at
all
pH
values
except
pH
12.
All
samples
meeting
the
goal
did
so
by
a
substantial
margin
(
concentration
<
0.01
mg/
L),
except
one
of
the
duplicates
at
pH
8.

The
treatment
process
of
Vendor
B
was
not
able
to
meet
the
treatment
goal
at
any
pH
values,
except
for
both
duplicates
of
one
sample
(
Phase
II,
pH
12).
7
The
treatment
process
of
Vendor
C
was
able
to
meet
the
goal
under
some
conditions.
In
general,
the
goal
could
be
met
at
higher
pH
and
in
Batch
#
2.
Both
duplicates
met
the
treatment
goal
in
Batch
#
2
at
pH
8,
but
only
one
met
the
goal
in
Batch
#
1
at
that
pH.
Both
duplicates
met
the
treatment
goal
in
Batch
#
2
at
pH
12,
but
neither
did
in
Batch
#
1
at
that
pH.
The
variability
in
performance
between
batches
shown
by
the
treatment
process
of
Vendor
C
is
not
substantially
different
from
that
shown
by
treatment
processes
of
other
vendors.
However,
the
treated
waste
provided
by
Vendor
C
produced
concentrations
in
the
CPLT
that
were
near
the
treatment
goal,
so
that
there
was
more
variation
in
whether
a
particular
sample
met
the
goal.
The
variability
in
performance
of
all
treated
wastes
indicates
the
problems
of
heterogeneity
of
the
waste
and/
or
variability
in
application
of
the
treatment
process.

The
treatment
process
of
Vendor
D
was
not
able
to
meet
the
goal,
except
at
higher
pH.
At
pH
12,
three
samples
met
the
goal
and
one
sample
was
at
the
goal
(
0.025
mg/
L).
However,
none
of
the
samples
at
pH
12
exceeded
the
goal
by
a
substantial
margin
(<
0.01
mg/
L).

Response:
EPA
agrees
with
the
reviewer's
assessment
of
the
data.
We
believe
that
the
heterogeneity
of
the
waste
and/
or
variability
in
application
of
the
treatment
process
noted
by
the
reviewer
for
Vendor
C
is
relevant
to
some
degree
to
all
of
the
vendors,
and
is
a
significant
factor
in
treating
granular,
complex
wastes
using
batch­
treatment
processes.
Therefore,
these
factors,
and
the
resulting
performance
variability,
must
be
examined
and
considered
when
evaluating
the
ability
of
a
commercial
treatment
technology
to
meet
a
performance
goal.

b)
Comparison
of
TCLP
to
constant
pH
leach
test
(
CPLT).
The
CPLT
is
similar
to
the
TCLP,
but
it
does
not
duplicate
all
conditions
of
the
TCLP.
In
addition
to
operating
at
different
pH,
the
CPLT
has
a
longer
leaching
time
(
14
days
compared
to
18
hours),
different
L/
S
ratio
(
20
L/
kg
dry
mass
compared
to
20
L/
kg
total
mass)
and
uses
a
different
leaching
solution
(
mixture
of
nitric
acid
and/
or
sodium
hydroxide
compared
to
acetic
acid
and
possibly
sodium
hydroxide).
These
differences
can
lead
to
observing
higher
or
lower
concentrations
in
the
CPLT
compared
to
those
measured
in
the
TCLP,
even
when
the
CPLT
is
at
the
pH
observed
in
the
TCLP.
Using
a
L/
S
ratio
defined
in
terms
of
dry
mass
rather
than
total
mass
will
result
in
a
greater
amount
of
waste
being
used
in
the
CPLT
per
unit
volume
of
leachate
compared
to
the
TCLP.
This
would
tend
to
lead
to
higher
concentrations
being
measured
in
the
CPLT.
A
longer
leaching
time
in
the
CPLT
would
tend
to
result
in
the
leaching
solution
approaching
more
closely
to
equilibrium
conditions
with
the
solids.
This
could
result
in
higher
or
lower
concentrations
being
observed,
because
concentrations
in
the
TCLP
test
can
be
increasing
or
decreasing
as
the
end
of
the
leaching
period
approaches.
Concentrations
would
tend
to
continuously
increase
for
components
whose
solubility
is
not
strongly
affected
by
pH
or
when
the
pH
of
the
leaching
fluid
does
not
change
appreciably.
However,
concentrations
of
compounds
that
are
strongly
affected
by
pH
would
tend
to
increase
initially
when
pH
is
low
and
then
decrease
as
pH
rises
in
the
leaching
fluid.
The
presence
of
nitrate
rather
than
acetic
acid/
acetate
could
affect
leaching
results
when
one
or
the
other
of
these
compounds
forms
stronger
complexes
with
a
metal
being
extracted.
8
The
treated
waste
provided
by
Vendor
A
showed
concentrations
in
the
TCLP
to
be
similar,
but
lower
than
concentrations
in
the
CPLT
when
interpolated
to
the
pH
of
the
TCLP.
However,
the
constant
pH
test
resulted
in
some
concentrations
at
other
pH
values
that
were
much
higher
than
observed
for
the
TCLP
at
pH
values
different
from
that
observed
in
the
TCLP.

The
treated
waste
provided
by
Vendor
B
showed
good
agreement
in
concentrations
measured
in
the
TCLP
and
in
the
CPLT,
when
concentrations
in
the
CPLT
are
interpolated
to
the
pH
of
the
TCLP.
However,
the
CPLT
resulted
in
some
concentrations
that
were
higher
and
lower
than
those
measured
in
the
TCLP,
when
measured
at
pH
values
different
from
those
observed
in
the
TCLP.

The
treated
waste
provided
by
Vendor
C
showed
similar
concentrations
measured
in
the
TCLP
and
in
the
CPLT,
when
concentrations
in
the
CPLT
are
interpolated
to
the
pH
of
the
TCLP.
However,
the
interpolated
concentrations
of
the
CPLT
tended
to
be
higher
than
those
in
the
TCLP.
However,
the
CPLT
resulted
in
some
concentrations
that
were
much
higher
than
those
observed
for
the
TCLP
at
pH
values
different
from
those
observed
in
the
TCLP.

The
treated
waste
provided
by
Vendor
D
showed
similar
concentrations
in
both
leach
tests,
when
compared
at
the
same
pH
and
when
the
result
in
the
CPLT
at
pH
10
for
Batch
#
1
is
considered
an
outlier.
This
point
should
be
considered
an
outlier
because
it
is
much
higher
than
the
general
trend
at
other
pH
values
for
Batch
#
1
and
very
different
from
that
observed
for
Batch
#
2
at
pH
10.
The
CPLT
resulted
in
some
concentrations
that
were
much
higher
than
those
observed
for
the
TCLP
at
pH
values
different
from
those
observed
in
the
TCLP.

In
general,
the
two
test
procedures
provided
similar
results
when
compared
at
the
same
pH.
In
some
cases,
the
concentrations
measured
in
the
TCLP
tended
to
be
a
little
lower
than
those
observed
by
interpolating
concentrations
measured
in
the
CPLT
to
the
pH
of
the
TCLP.
This
could
be
due
to
the
fact
that
the
TCLP
has
a
higher
effective
L/
S
and
shorter
leaching
time
than
the
CPLT.
The
CPLT
also
produced
concentrations
at
other
pH
values
that
could
be
much
higher
than
those
measured
in
the
TCLP.

Response:
EPA
notes
that
the
reviewer
has
simply
summarized
the
study
results,
and
that
no
response
is
necessary.

Supplementary
Information
Question
1:
Are
you
aware
of
any
other
data/
studies
that
are
relevant
to
the
assessment
of
stabilized
mercury­
bearing
wastes
and
the
behavior
of
these
wastes
in
the
environment?

Reviewer
#
1:
No,
I
am
not
aware
of
any
other
data/
studies
that
are
similar
in
nature
to
this
study.

Reviewer
#
2:
This
report
does
not
have
a
list
of
baseline
references,
so
the
question
is
very
broad.
A
start
would
be
the
studies
completed
for
EPA
or
used
by
EPA
in
previous
rule­
making.
Second
would
be
a
literature
review
using
appropriate
keywords
9
Response:
A
bibliography
(
provided
by
Reviewer
#
3)
was
included
in
a
final
revision
of
the
report.

Reviewer
#
3:
The
following
is
list
of
articles
relevant
to
both
studies:

"
Stabilization/
solidification
(
S/
S)
of
mercury­
containing
wastes
using
reactivated
carbon
and
Portland
cement",
Zhang,
Jian;
Bishop,
Paul
L.
Journal
of
Hazardous
Materials
(
2002),
92(
2),
199­
212.
"
Sulfide­
induced
stabilization
and
leachability
studies
of
mercury
containing
wastes",
Piao,
Haishan;
Bishop,
Paul,
Abstracts
of
Papers,
223rd
ACS
National
Meeting,
Orlando,
FL,
United
States,
April
7­
11,
2002
(
2002),
ENVR­
207.
"
Phosphate­
induced
mercury
stabilization",
Zhang,
Jian;
Bishop,
Paul
L.,
Preprints
of
Extended
Abstracts
presented
at
the
ACS
National
Meeting,
American
Chemical
Society,
Division
of
Environmental
Chemistry
(
2001),
41(
1),
422­
424.
"
Sulfide­
induced
mercury
stabilization",
Piao,
Haishan;
Bishop,
Paul
L.,
Preprints
of
Extended
Abstracts
presented
at
the
ACS
National
Meeting,
American
Chemical
Society,
Division
of
Environmental
Chemistry
(
2001),
41(
1),
428­
431.
"
Stabilization
of
radioactively
contaminated
elemental
mercury
wastes",
Stewart,
Robin;
Broderick,
Tom;
Litz,
John;
Brown,
Cliff;
Faucette,
Andrea.,
Proceedings
of
the
International
Conference
on
Decommissioning
and
Decontamination
and
on
Nuclear
and
Hazardous
Waste
Management,
Denver,
Sept.
13­
18,
1998
(
1998),
3
33­
36.
"
Mercury
stabilization
in
chemically
bonded
phosphate
ceramics",
Wagh,
Arun
S.;
Jeong,
Seung­
Young;
Singh,
Dileep,
Ceramic
Transactions
(
1998),
87(
Environmental
Issues
and
Waste
Management
Technologies
in
the
Ceramic
and
Nuclear
Industries
III),
63­
73.
"
A
Framework
for
Risk
Assessment
of
Disposal
of
Wastes
Treated
by
Solidification/
Stabilization",
Batchelor,
B.,
Environmental
Engineering
Science,
14(
1):
3­
13,
1997.
"
A
study
of
immobilization
of
four
heavy
metals
by
solidification/
stabilizatioin
with
Portland
cement",
Susan
A.
Trussell,
Ph.
D.
Dissertation,
Texas
A&
M
University,
College
Station,
Texas,
1994.
"
Immobilization
of
chromium
and
mercury
from
industrial
wastes",
Wasay,
S.
A.;
Das,
H.
A.
,
J.
Environ.
Sci.
Health,
Part
A
(
1993),
A28(
2),
285­
97.
Chemical
Fixation
and
Solidification
of
Hazardous
Wastes,
Jesse
R.
Conner,
Van
Nostrand
Reinhold,
New
York,
1990.
"
An
investigation
of
mercury
solidification
and
stabilization
in
portland
cement
using
x­
ray
photoelectron
spectroscopy
and
energy
dispersive
spectroscopy",
McWhinney,
Hylton
G.;
Cocke,
David
L.;
Balke,
Karl;
Ortego,
J.
Dale.,
Cem.
Concr.
Res.
(
1990),
20(
1),
79­
91.
"
Studies
of
zinc,
cadmium
and
mercury
stabilization
in
OPC/
PFA
mixtures",
Poon,
C.
S.;
Perry,
R.,
Mater.
Res.
Soc.
Symp.
Proc.
(
1987),
86(
Fly
Ash
Coal
Convers.
By­
Prod.),
67­
76.
"
Permeability
study
on
the
cement
based
solidification
process
for
the
disposal
of
hazardous
wastes",
Poon,
C.
S.;
Clark,
A.
I.;
Perry,
R.;
Barker,
A.
P.;
Barnes,
P.,
Cem.
Concr.
Res.
(
1986),
16(
2),
161­
72.
"
Mechanisms
of
metal
fixation
and
leaching
by
cement
based
fixation
processes",
Poon,
C.
S.;
Clark,
A.
I.;
Peters,
C.
J.;
Perry,
R.,
Waste
Manage.
Res.
(
1985),
3(
2),
127­
42.
10
"
Mechanisms
of
metal
stabilization
by
cement
based
fixation
processes",
Poon,
C.
S.;
Peters,
C.
J.;
Perry,
R.;
Barnes,
P.;
Barker,
A.
P.,
Sci.
Total
Environ.
(
1985),
41(
1),
55­
71.

A
database
is
being
prepared
that
will
contain
information
on
many
characteristics
of
wastes.
This
will
include
those
containing
mercury.
The
final
report
has
not
been
prepared
but
information
is
available
at:
http://
www.
concrete.
cv.
ic.
ac.
uk/
iscowaa/
nnapics/
intro.
html
Response:
The
bibliography
provided
by
the
Reviewer
was
included
in
a
final
revision
of
the
report.

Question
2:
With
regard
to
the
disposal
of
treated
mercury
wastes,
are
additional
studies
warranted
for
other
factors
that
impact
solubility
or
affect
ability
to
leach,
such
as
use
of
macroencapsulation?
If
you
believe
that
additional
studies
are
needed,
please
explain
why.

Reviewer
#
1:
Yes.
This
study
was
conducted
by
preparing
and
evaluating
a
surrogate
waste
sample.
However,
no
data/
results
have
been
generated
to
show
that
stabilization
and
leaching
characteristics
of
actual
wastes
would
yield
similar
results
when
tested
in
a
similar
manner.
I
suggest
that
two
or
more
wastes
containing
over
260
mg/
kg
of
mercury
be
subjected
to
stabilization
and
leaching
by
TCLP
as
well
as
by
the
constant
pH
leaching
protocols.
If
those
test
results
show
that
leachates
do
not
exceed
0.025
mg/
L
goal
at
all
pH
values
then
selection
of
stabilization
technology
would
not
require
any
site­
specific
considerations.

Response:
The
additional
study
proposed
by
the
Reviewer
will
be
considered
as
additional
resources
become
available,
however,
EPA
believes
that
it
is
reasonable
to
expect
the
surrogate
waste
constructed
for
this
study
to
be
representative
of
actual
wastes,
both
with
respect
to
composition
and
response
to
stabilization.

Reviewer
#
2:
An
additional
study
is
needed
to
supplement
this
report,
particularly
extractions
up
to
at
least
pH
12.5.
If
the
mercuric
selenide
process
is
considered
a
viable
technology,
then
mercuric
selenide­
containing
waste
should
be
evaluated
over
the
range
of
pH
2­
12.5
and
with
varied
chloride
content
in
the
leachate.
Additional
studies
on
other
factors
could
be
done,
but
the
priorities
seem
to
be:
pH
effects
(
2­
12.5),
leachate
composition
(
e.
g.,
chloride)
effects,
and
redox
effects.
A
decision
should
be
made
about
how
accurately
a
waste
treatment
evaluation
needs
to
be,
then
deciding
on
the
relative
importance
of
variables.

Response:
The
reviewer
has
placed
undue
significance
on
pH
12.5.
Few
Landfills
exhibit
such
extreme
conditions.
We
believe
the
trend
of
performance
can
be
adequately
established
with
testing
in
the
pH
2
­
12
range.
However,
if
disposal
under
extreme
conditions
were
planned,
then
we
concur
that
testing
should
encompass
such
conditions
with
testing
at
pH
13
or
above.
The
additional
studies
proposed
by
the
Reviewer
will
be
considered
as
additional
resources
become
available.

Reviewer
#
3:
These
studies
have
adequately
demonstrated
that
a
goal
of
0.025
mg/
L
in
the
TCLP
can
be
met
by
existing
stabilization
technologies,
both
for
a
surrogate
waste
containing
various
11
forms
of
mercury
at
a
total
concentration
of
5,000
mg/
kg
and
for
elemental
mercury.
However,
meeting
this
goal
does
not
insure
that
adequate
protection
of
human
health
and
the
environment
is
assured
for
all
conditions
of
waste
disposal.
However,
this
statement
is
not
limited
to
mercury
wastes,
but
is
a
limitation
of
the
TCLP
for
all
hazardous
constituents.
Therefore,
additional
studies
are
not
warranted
to
determine
if
existing
technologies
can
meet
a
TCLP
goal
of
0.025
mg/
L
for
wastes
that
contain
mercury
at
concentrations
above
260
mg/
kg.
However,
additional
studies
are
warranted
to
develop
characterization
methods
and
analytical
techniques
that
will
insure
safe
disposal
of
hazardous
wastes
containing
toxic
materials
including
mercury
under
a
range
of
site­
specific
disposal
conditions.

Response:
The
Agency
is
currently
considering
alternative
leaching
technologies
that
will
be
applicable
to
a
broad
spectrum
of
hazardous
wastes,
including
those
containing
mercury.
The
Agency
is
also
developing
guidance
for
the
use
of
leachate
protocols
in
site­
specific
hazard
assessment.
As
these
considerations
are
completed,
and
new
approaches
developed,
the
results
will
be
published.

Question
3:
Do
you
agree
that
the
following
statement
is
supported
by
the
research
results?

(
a)
Site­
specific
disposal
conditions
must
be
considered
along
with
appropriate
treatment
technology
as
decisions
are
made
about
disposal
of
mercury
wastes.

Reviewer
#
1:
I
partially
agree.
As
indicated
in
my
response
to
the
foregoing
Question
2,
the
answer
to
this
question
is
that
it
depends
on
the
results
obtained
from
carrying
out
the
recommended
testing
of
actual
wastes.
However,
based
on
the
results
presented
in
this
report,
it
seems
that
pH
was
the
only
environmental
parameter
tested
for
the
evaluation
of
effectiveness.
The
Vendor
A
technology
will
require
that
the
site
be
evaluated
to
determine
if
the
leaching
fluid
that
will
be
infiltrating
through
the
stabilized
waste
has
a
pH
of
10
or
less.
No
other
disposal
conditions
would
need
to
be
considered.
In
my
technical
evaluation
of
the
test
results
presented
in
the
report,
I
see
that
Vendor
A
technology
should
be
used
because
of
its
effectiveness
under
a
large
range
of
pH
conditions.

Response:
pH
was
the
only
environmental
variable
evaluated
in
this
study.
EPA
acknowledges
that
there
are
other
variables,
but
believes
that
pH
is
certainly
a
significant
variable.
The
Reviewer
acknowledges
that
the
pH
of
the
leachate
in
the
landfill
cell,
a
site­
specific
condition,
must
be
considered
when
selecting
a
technology.
EPA
believes
that
this
supports
the
conclusion
that
"
Site­
specific
disposal
conditions
must
be
considered
along
with
appropriate
treatment
technology
as
decisions
are
made
about
disposal
of
mercury
wastes.".

Reviewer
#
2:
No.
The
study
provides
useful
data
on
pH
effects,
but
it
does
not
provide
adequate
data
to
support
an
absolute
requirement
for
site­
specific
data.
An
alternative
to
using
sitespecific
conditions
is
a
robust
treatment
standard
which
addresses
the
most
important
variables.
A
major
implementation
problem
with
requiring
site­
specific
conditions
is
the
regulatory
feasibility
of
using
site­
specific
information.
For
any
disposal
of
hazardous
wastes,
treated
or
untreated,
it
is
scientifically
preferable
to
use
site­
specific
conditions
as
well
as
the
waste
12
properties.
It
is
not
obvious
that
using
site­
specific
data
would
be
better
than
non­
site
specific
approaches
to
meet
the
public
health
and
environmental
protection
goals,
in
part
because
those
specific
goals
are
not
stated
in
this
report.

Response:
We
agree
that
it
is
scientifically
preferable
to
use
site­
specific
conditions
as
well
as
the
waste
properties
to
assess
disposal
options.
EPA
believes
that
consideration
of
site­
specific
disposal
conditions
along
with
appropriate
treatment
technology
information
is
the
best
alternative
when
making
environmentally
sound
decisions
about
the
disposition
of
these
high
mercury
stabilized
wastes.
As
the
reviewer
correctly
notes,
implementation
of
such
requirements
into
a
regulatory
framework
would
be
problematic.
We
believe
that
the
reviewer's
suggestion
of
using
a
robust
treatment
standard
that
addresses
only
the
most
important
variables
would
be
equally
problematic
to
implement
on
a
national
basis.

Reviewer
#
3:
These
research
results
do
support
this
statement,
because
they
demonstrate
that
pH
can
have
an
important
impact
on
the
amount
of
mercury
leached
from
treated
wastes.
The
pH
of
a
leaching
fluid
can
be
very
different
under
different
disposal
conditions.
However,
the
research
results
do
not
prove
the
statement,
because
there
could
be
conditions
under
which
a
waste
could
be
characterized
so
that
site­
specific
disposal
conditions
would
not
be
required
to
insure
a
reasonable
degree
of
confidence
in
protection
of
human
health
and
the
environment.

Response:
EPA
acknowledges
the
difference
noted
by
the
Reviewer
between
data
"
supporting"
and
"
proving"
a
premise.
The
Agency
does
not
anticipate
having
sufficient
resources
available
to
investigate
all
of
the
characterizations
conditions
possible
in
order
to
definitively
prove
or
disprove
the
hypothesis.

Question
4:
Do
you
have
any
other
comments?

Reviewer
#
1
No.

Reviewer
#
2:
Table
3­
1
presumably
shows
target
concentrations
and
not
actual
measured
concentrations.
Section
3.3.1
lists
the
worker
protection
standard
as
0.05
g/
m3,
but
Section
lists
the
TLV
as
0.025
mg/
m3.
The
conclusions
in
Section
5.6
refer
to
"...
waste
bulk
elemental
mercury..."
although
this
study
included
several
forms
of
mercury.

Response:
The
editorial
corrections
suggested
by
the
reviewer
were
incorporated
in
a
final
revision
to
the
report.

Reviewer
#
3:
The
following
are
suggestions
for
corrections
to
the
report:
C
(
Various
places)
The
relationship
of
ALTER
and
the
University
of
Cincinnati
should
be
clarified.
It
appears
that
the
two
are
used
interchangeably.
C
(
p.
2­
5,
bullet
3)
should
be
"<
260
ppm"
C
(
p.
3­
4,
line
5
from
bottom
and
elsewhere)
Provide
units
for
liquid/
solid
ratio.
C
(
p.
5­
1,
Table
5­
1
and
others)
Percentages
should
be
reported
with
no
more
significant
digits
than
the
measurements
upon
which
they
are
based.
13
C
(
p.
5­
1,
Table
5­
1
and
others)
The
leaching
fluid
used
in
the
TCLP
tests
should
be
specified.
C
(
p.
5­
5,
Table
5­
4,
columns
2,3,6,7)
Replace
"
3/
4"
with
blank
or
other
indication
that
presenting
the
percent
leached
is
not
appropriate
for
a
blank.

Response:
The
editorial
corrections
suggested
by
the
reviewer
were
incorporated
in
a
final
revision
to
the
report.
