MEMORANDUM
To:
Samantha
Lewis,
Shari
Barash
EPA/
OST/
EAD
From:
Jim
Parker,
Indra
Mitra
Date:
January
23,
2004
Subject:
Supplementary
Technical
Analysis
For
Phosphorus
Removal
In
the
EPA
cost
model,
a
Alum:
Phosphorus
(
Al:
P)
molar
ratio
of
1.8
is
used
for
costing
facilities.
The
purpose
of
this
memorandum
is
to
discuss
the
effect
of
costs
when
Al:
P
ratio
is
increased
beyond
1.8.
Preliminary
costs
for
Option
2.5+
P
were
estimated
for
8
meat
and
8
poultry
facilities
for
Al:
P
ratio
of
1.8,
2.0,
and
2.5.
For
the
cost
runs
for
Al:
P
ratio
of
2
and
2.5,
the
increased
annualized
costs
over
costs
corresponding
to
Al:
P
ratio
of
1.8
are
shown
in
Table
1.
The
results
show
that
increasing
the
Al:
P
ratio
to
greater
than
2
may
increase
the
annualized
costs
per
poultry
facility
by
more
than
$
24,000.
Similarly,
increasing
the
Al:
P
ratio
to
greater
than
2
may
increase
the
annualized
costs
per
meat
facility
(
subcategory
A­
D)
by
more
than
$
107,000.

The
reaction
of
alum
with
phosphate
can
be
described
by:

Al
2(
SO
4)
3.14H
2
O
+
2
PO
4
­
3
­­>
2
AlPO
4
(
ppt)
+
3
SO
4
­
2
+
14
H
2
O
Based
on
stoichiometry,
the
above
reaction
predicts
that
the
required
Al:
P
ratio
is
0.87:
1.

where:
Al
=
moles
of
aluminum
P
=
moles
of
phosphorus
removed
However,
in
practice,
the
quantities
of
alum
required
are
higher
than
what
the
stoichiometry
would
predict.
This
is
because
alum
participates
in
competing
reactions
with
various
constituents.
Among
the
most
notable
factors
that
affect
the
actual
quantity
of
alum
are:
the
alkalinity
and
final
pH
of
the
wastewater,
ionic
constituents,
microorganism,
colloidal
species,
mixing
intensity,
and
other
physical
conditions
in
the
treatment
plant.
The
optimum
pH
for
phosphorus
removal
using
alum
is
in
the
range
of
5.5­
6.5.
Although
strong
acids
could
be
used
to
lower
the
pH
to
the
optimum
point,
it
may
be
simpler
to
use
a
higher
alum
dosage
to
depress
the
pH.

The
dose
observed
at
municipal
plants
varies
between
0.3
and
4.6.
Based
on
these
data
and
data
available
in
literature,
Al:
P
ratio
of
1.8
is
used
in
the
model.
However,
any
value
between
1.7
and
2.5
looks
may
be
considered
reasonable
for
costing
purposes.
It
should
be
noted
that
the
actual
alum
dose
required
for
a
facility
is
normally
determined
from
experiments
(
jar
tests).
Since
wastewater
characteristics
vary
from
facility
to
facility,
jar
tests
are
recommended
for
determining
alum
dose.

Table
1
Increased
Annualized
Costs
For
Different
Al:
P
Ratios
Samantha
Lewis
Shari
Barash
Page
2
January
23,
2004
Facility
Increase
In
Annualized
Costs
($/
year)

Al:
P
=
2
Al:
P
=
2.5
Poultry
P1
$
36,092
$
126,321
P2
$
69,000
$
241,355
P3
$
13,924
$
48,736
P4
$
21,314
$
71,903
P5
$
17,956
$
225,609
P6
$
10,619
$
37,166
P7
$
22,733
$
79,566
P8
$
5,450
$
18,834
Average
$
24,636
$
106,186
Meat
M1
$
62,725
$
219,536
M2
$
122,624
$
429,183
M3
$
254,461
$
890,614
M4
$
12,165
$
42,576
M5
$
188,762
$
660,668
M6
$
6,929
$
24,251
M7
$
160,492
$
561,356
M8
$
55,775
$
195,214
Average
$
107,992
$
377,925
