Demineralization of whey by means of ion exchange and electrodialysis


Houldsworth, D.W.

International Journal of Dairy Technology 33(2): 45-51

1980


Regenerated
Cation
H
+
I /
H+
H
+
1-1
1-
Na*Cl
-
+
H
+
WO
-
+
Na
+
Anion
OH
-
OH
-
\
I
OH
-
OH
-
H
+
Cl
-
+
OH
-
--ow
H
2
0
+
C
t
OH=
—OH
-
OH
-
OH
-
Saturated
Na
4
Na
+
N
a
+
/
Na
+
—N
Cl
-
Cl
-
I
Cl
-
/
C1
-
—1
1—
Cl'
\
\
Na
+
NaNa
+
Cl
-
Cl
-
No
+
i
Cl
-
H
+
Cl
-
+
Na
+
NeCt
-
+H
+
i
Na
.
OH
-
TWO-DAY
SYMPOSIUM
22nd
and
23rd
October,
1979,
at
the
Scientific
Societies
Lecture
Theatre,
Savile
Row,
London
W1
Subject:
Whey
technology
Demineralization
of
whey
by
means
of
ion
exchange
and
electrodialysis
By
D.
W.
HOULDSWORTH
A.P.V.
International
Ltd.,
Crawley,
West
Sussex
RH10
2QB
The
paper
is
concerned
with
two
different
methods
in
the
demineralization
of
whey
and
the
economics
of
the
two
processes
ion
exchange
and
electrodialysis
are
assessed.
The
operation
of
each
system
is
described
in
full
and
the
various
advantages,
disadvantages
and
limitations
are
evaluated.
Operating
concentration,
cleaning,
energy
costs,
effluent
disposal,
yield
and
product
acceptability
for
the
two
processes
are
discussed.
Appendices
showing
operating
costs
in
detail
are
included.
(Editor's
summary)
The
objective
of
this
paper
is
to
present
an
economic
assessment
of
two
different
methods
of
removing
salts
from
whey,
based
on
a
plant
size
of
50,000
g/day
(227,000
1/day)
and
demineralizing
from
50
to
90
per
cent.
I
have
taken
the
main
contenders
in
the
whey
deminer-
alizing
field
for
this
presentation
as
defined
by
the
largest
number
of
commercially
operating
installations.
These
are:
1.
Ion
exchange
Applexion,
3
Avenue
de
la
Mauldre,
78680
Epone,
France.
(87
commercial
plants;
53
in
the
food
industry
and
21
in
the
dairy
industry).
2.
Electrodialysis
SRTI,
Route
de
Guyancourt,
B.P.
No.
10,
78530
Buc,
France.
(22
commercial
plants;
17
in
the
dairy
industry).
Ionics
Inc.,
65
Grove
Street,
Watertown,
Mass.
02172,
USA.
(25
E.D.
lines
in
the
dairy
industry).
Inevitably
a
number
of
other
demineralizing
companies
active
in
the
dairy
industry
have
been
excluded,
but
I
believe
that
the
above
three
represent
a
realistic
cross-
section
of
the
developed
demineralizing
processes.
The
information
in
this
paper
relates
specifically
to
the
UK
and
the
costing
is
based
on
UK
prices
as
at
1st
October,
1979.
Chemical
material
costs,
electrical
costs
and
water
and
effluent
costs
are
changing
very
rapidly
at
present
and
depend
to
a
major
extent
on
geographical
location
and
local
conditions.
For
this
reason
I
would
emphasize
that
these
costs
are
indicative
only
and
would
need
further
study
for
any
particular
project,
using
local
costing.
It
is
always
difficult
to
ensure
a
fair
and
realistic
com-
parison
between
two
different
processes
as
the
extent
of
equipment
supply,
pre-
and
post-treatment
required
and
sometimes
the
overall
process
yields
are
difficult
to
define
accurately
on
an
equivalent
basis.
Appendix
2
outlines
the
extent
of
supply
for
both
electrodialysis
and
ion
exchange.
Throughout
this
comparison,
figures
supplied
by
the
system
manufacturers
themselves
have
been
used.
Before
dealing
with
the
economics
of
the
two
processes,
let
me
briefly
define
both
processes,
although
I
am
certain
that
most
of
you
will
be
familiar
with
them.
Fig.
1.
Simplified
model
of
ion
exchange
Ion
exchange
Ion
exchange
resins
as
used
for
whey
demineralization
are
in
the
physical
form
of
small
beads,
typically
0.4-0.8
mm
diameter.
By
varying
the
ratio
of
component
materials
(principally
polystyrene
and
divinyl
benzene)
and
the
method
and
degree
of
cross-linking
these
materials,
a
very
Journal
of
the
Society
of
Dairy
Technology,
Vol.
33,
No.
2,
April
1980
45
Anion
exchanger
H
+
-i-
OH
Single
line
6
hour
cycle
Absorption
1
Regeneration
Two
lines
Absorption
I
Regeneration
Regeneration
I
Absorption
I
Regeneration
Absorption
I
Regeneration
L1
L2
Total
Three
lines
Absorption
I
Regeneration
Regeneration
I
Absorption
1
Regeneration
Regeneration
I
Absorption
Absorption
L1
L2
L3
Total
By—pass
loop
Ci
o
lize
d
w
ile
ca
Dem
in
whey
to
storage
pH
or
conductivity
meter
95'4
demineralized
whey
Cation
exchanger
0
Deca
t
io
niz
H
+
-1-C1
-
Fig.
2.
Diagram
of
ion
ex-
change
line
wide
range
of
properties
can
be
produced
in
the
resultant
beads.
A
useful
model
in
visualizing
the
process
is
to
consider
the
beads
of
resin
as
having
a
large
number
of
firmly
attached
bonds
on
their
surface
which
can
be
made
to
absorb
(reversibly)
one
or
other
of
the
ionic
species
sur-
rounding
it,
dependent
on
local
conditions
(Fig.
1).
A
cationic
resin
in
this
model
would
be
a
small
sphere
with
positively
charged
ions
attached
to
the
bonding
sites,
Absorption
2
hours
Regeneration
4
hours
Fig.
3.
Plant
utilization
scheme
such
as
sodium,
potassium
and
calcium
being
absorbed
in
to
the
resins
displacing
the
H+
ions
in
the
process.
The
anions
would
pass
through
the
bed
unaffected
.
Subsequent
passage
of
this
decationized
whey
through
the
anion
resin
would
absorb
anions
such
as
chloride
and
sulphate
displacing
OH
-
ions
in
the
process
and
result
in
demineralized
whey
exiting
from
the
anion
resin
column.
This
transfer
of
whey
through
the
resin
beds
in
series
con-
tinues
until
most
of
the
resin
bonding
sites
are
filled
or
saturated
by
cations
or
anions
from
the
whey.
At
this
point
the
resin
beds
are
purged
of
whey,
washed with
water
and
regenerated
by
means
of
acid
and
alkali
solu-
tions.
These
solutions
are
sufficiently
concentrated
to
re-
move
the
absorbed
cations
and
anions
and
replace
them
by
H+
and
OH
-
ions
bringing
them
back
to
their
previous
state.
Following
thorough
washing
with
clean
water,
a
fresh
batch
of
whey
is
pumped
to
the
resin
beds
and
the
process
repeated,
see
Fig.
2.
A
typical
cycle
would
be
two
hours
absorption,
four
hours
regeneration,
giving
six
hours
total
per
cycle
and
four
cycles/day.
The
columns
are
made
of
rubber-lined
mild
steel,
externally
painted.
All
operations
are
automatic,
including
regeneration
controlled
by
simple
diode
matrix
automation.
For
more
continuous
operation
(Fig.
3)
two
demineraliz-
ing
lines
each
containing
one
cation
and
one
anion
column
are
used,
the
second
line
going
onto
production
as
the
first
starts
regeneration,
gives
effectively
four
hours
on
pro-
duction
and
two
hours
down
time
for
regeneration.
Three
parallel
lines
would
give
continuous
production,
but
in
commercial
practice,
it
has
been
found
that
one
or
two
lines,
depending
on
the
scale
of
operation,
gives
optimum
economic
return.
g
say
H+
ions.
Similarly
an
anionic
resin
would
be
a
small
sphere
with
negatively
charged
ions
attached,
say
OH
-
ions.
Passing
undemineralized
whey
over
a
bed
of
cation
resins
would
result
in
almost
all
the
cations
in
the
whey,
Fig.
4.
Ion
exchange
demineralization
plant
46
Journal
of
the
Society
of
Dairy
Technology,
Vol.
33,
No.
2,
April
1980
II
41=E1
MIMI
MOM 01•11
Salt
solution
NIM MIN=
C
I
.1•.
....
r
I
A
1
4
!
_
_
_
C
_
_
_
I
A
Cathode
Cation
membr
Na
+
Na
+
n
Na
+
N
ak.
N
4
I
Cl
-
C
1
—,
—71
46"
41/•
t
I
I
S
I
I
_
I
Fig.
5.
Diagram
of
electro-
dialysis
process
Anion
membrane
ane
Anode
Cl
-
Product
(Whey
with
NaCI)
Conc
salt
solution
...
der
m.e.•
aaaaaaaaaaa ••••
Demineralized
product
Whey
emerging
from
an
ion
exchange
line
will
be
found
to
be
94-95
per
cent
demineralized
and
to
achieve
less
than
this
figure,
a
by-pass
arrangement
is
used
to
mix
undemin-
eralized
whey
with
fully
demineralized
whey
in
the
correct
ratio.
For
the
sake
of
conformity
with
the
electrodialysis
costings,
90
per
cent
demineralization
by
ion
exchange
has
been
assumed,
although
the
actual
level
is
higher
than
this
(Fig.
4).
Electrodialysis
In
electrodialysis,
a
number
of
membrane
cells
are
formed,
each
cell
being
bounded
by
a
cationic
membrane
on
one
side
and
an
anionic
membrane
on
the
other
and
with
a
membrane
spacer
in
between.
The
membrane
stack
formed
by
a
number
of
cells
has
entry
and
exit
ports
analogous
to
the
plate
heat
exchanger
which
enable
parallel
or
series
flow
to
be
constructed
as
required.
Whey
flows
along
alter-
nate
channels,
typically
1
mm
deep,
defined
by
the
mem-
brane
spacer,
and
a
dilute
salt
solution
flows
between
each
of
the
above
cells
separated
from
the
whey
by
the
selective
membranes.
The
dilute
salt
solution
is
the
flushing
solution
(Fig.
5).
The
entire
assembly
is
placed
between
a
series
of
elec-
trodes
which
provide
a
DC
electric
field
perpendicular
to
the
membrane
surfaces
as
the
whey
is
recirculated
round
the
system.
Under
the
influence
of
the
electric
field,
cations
migrate
towards
and
through
the
cation
membranes
and
into
the
flushing
solution.
Similarly
the
anions
migrate
towards
the
anionic
membrane,
through
it
and
into
the
flushing
solution.
In
this
way
the
concentration
of
cations
and
anions
in
the
whey
falls
while
the
concentration
in
the
flushing
solution
rises.
This
flushing
solution
must
be
di-
luted
as
the
process
continues
and
dilution
water
is
added
and
the
overflow
salt
solution
passes
to
drain.
As
the
ionic
concentration
in
the
whey
falls
the
con-
ductivity
of
the
whey
is
reduced
and
it
becomes
pro-
gressively
more
difficult
to
remove
further
quantities
of
salt.
The
applied
voltage
is
increased
during
the
run
to
compensate
to
some
extent
for
this
effect.
To
obtain
significant
demineralization
levels
it
is
necess-
ary
to
recycle
the
whey
through
the
plant
a
number
of
times
and
this
is
performed
via
a
batch
tank
with
a
con-
ductivity
meter
attached,
through
which
the
whey
is
re-
circulated
until
a
predetermined
conductivity
level
is
achieved.
At
this
point
the
demineralized
whey
is
pumped
out
and
a
fresh
batch
of
undemineralized
whey
pumped
in
(Figs.
6
and
7).
ll
ik
P
1..
taw
r
01‘..
0
4
,
Anumpover,
Fig.
6.
Ionics
standard
whey
plant
Applications
Demineralized
whey
powders
from
50
to
90
per
cent
have
applications
in
a
very
wide
range
of
food
industries
includ-
ing
baby
food
formulations,
ice
cream,
sauces,
sweets,
soft
drinks,
powder
cake
and
pudding
mixes,
cereals,
pasta
and
a
range
of
dietary
products.
New
applications
are
becoming
more
interesting
when
combined
with
processes
such
as
ultrafiltration
enabling
an
'engineered'
whey
powder
with
a
very
wide
range
of
pro-
tein,
lactose
and
ash
specifications
to
be
produced.
•••
6
.11.11.1p.h.
Fig.
7.
SRTI
standard
whey
plant
Journal
of
the
Society
of
Dairy
Technology,
Vol.
33,
No.
2,
April
1980
47
The
use
of
electrodialysis
and
ion
exchange
to
deminer-
alize
whey
permeate
is
a
further
area
where
progress
is
being
made
commercially,
either
for
the
production
of
low
ash
lactose
from
permeate
or
as
a
pre-treatment
to
the
various
lactose
hydrolysis
techniques
now
becoming
available.
The
practical
operating
differences
and
similarities
for
the
two
processes
are
outlined
below:
Operating
concentration
The
conductivity
of
a
whey
solution
is
a
function
of
the
concentrations
of
salts
in
it,
and
electrodialysis
operated
most
efficiently
with
a
solution
of
high
conductivity.
Pre-
concentration
of
whey
prior
to
electrodialysis
will
help
in
this
respect,
reducing
both
capital
and
running
costs.
The
SRTI
electrodialysis
system
operation
is
optimized
at
a
concentration
of
18
per
cent
total
solids
(TS)
while
Ionics
prefer
23-28
per
cent
total
solids.
No
account
of
precon-
centration
costs
have
been
taken
in
this
analysis
as
in
most
instances
concentration
prior
to
drying
is
the
next
stage
following
demineralization.
It
could
well
be
argued
that
a
concentration
prior
to
demineralizing
up
to
18-28
per
cent
TS
followed
by
further
concentration
after
demineralizing
the
production
of
50
per
cent
demineralized
whey,
but
this
tends
to
be
a
little
more
expensive
to
operate.
Thorough
clarification
is
required
with
electrodialysis
to
remove
casein
fines
in
particular,
and
reduce
membrane
fouling.
Ion
exchange
normally
employs
a
screening
tech-
nique
and
clarification
is
not
essential.
Cleaning
Ion
exchange
systems
are
not
cleaned
in
place
in
the
conventional
manner,
but
are
automatically
cleaned
during
the
backwash
and
regeneration
period.
For
additional
safety
a
daily
rinse
with
a
proprietary
sterilizing
agent
such
as
Sterex
(a
minimal
oxidizing
chlorine
source)
ensures
that
any
organisms
which
have
survived
the
severe
pH
swings
inherent
in
regeneration
are
effectively
controlled.
The
delivery
and
product
pipework
around
the
plant
must
be
cleaned
as
part
of
a
conventional
cleaning-in-place
(CIP)
circuit
however.
Electrodialysis
allows
for
a
cleaning
period
of
from
two
(SRTI)
to
six
(Ionics)
hours/day
to
ensure
clean
mem-
branes
for
the
next
day's
production. Cleaning
is
by
means
of
acid
and
alkali
washes.
TABLE
1
Salts
in
effluent
with
ion
exchange
and
electrodialysis
Source
of
salts
Ionics
(E.
D.)
SRTI
(E.D.)
Applexion
(I.E.)
30%
Demin.
90%
Demin.
50%
Demin.
90
%
Demin.
50
%
Demin.
94
%
Demin.
Ash
extracted
from
whey
kg/d
703
1,265
703
1,265
703
1,321
Chemical
used
kg/d
249
843
200
350
1,456
2,912
Total
ash
kg/d
952
2,108
903
1,615
2,159
4,233
Total
Demineralizer
effluent
m
3
/d
151
640
125
230
147
294
Average
salt
in
effluent
ppm
6,300
3,300
7,200
7,000
14,700
14,400
but
prior
to
drying
is
intrinsically
a
less
efficient
process
than
a
single
concentration
stage,
but
this
factor
has
been
ignored
in
this
presentation.
Electrodialysis
systems
can
of
course
operate
on
un-
concentrated
whey
but
the
capital
cost
and
running
costs
of
such
a
plant
would
be
higher,
typically
15
per
cent
higher
at
50
per
cent
demineralization
and
30
per
cent
higher
at
90
per
cent
demineralization.
Ion
exchange
systems
on
the
other
hand
normally
operate
on
unconcentrated
whey
but
can
deal
with
whey
preconcentrated
up
to
18
per
cent
TS
although
no
great
economic
advantage
is
obtained
by
so
doing.
Operating
technique
Ion
exchange
utilizes
a
once
through
whey
transfer
system
with
a
typical
residence
time
of
20
minutes.
In
addition
the
whey
is
normally
pre-cooled
to
say
10°C
for
optimum
pro-
cess
yield
reasons,
and
this
in
itself
substantially
limits
bacterial
action.
Pasteurizing
at
65°C
for
15
seconds
is
recommended
as
pasteurizing
at
high
temperatures
or
holding
for
longer
periods
of
time
tends
to
reduce
the
overall
protein
yield.
Electrodialysis,
to
achieve
a
reasonable
degree
of
de-
mineralization,
requires
that
the
whey
be
recirculated
via
a
batch
tank
until
the
required
degree
of
demineralization
has
been
achieved.
This
takes
place,
following
conventional
pasteurizing,
at
a
temperature
of
between
30°C
and
45°C
depending
on
the
system.
Operation
at
lower
temperatures
to
avoid
the
main
bacteriological
growth
area
results
in
a
much
reduced
plant
capacity.
The
recirculation
time
may
be
as
long
as
six
hours
when
running
at
90
per
cent
demin-
eralization.
Ionics
have
developed
a
continuous
plant
for
Labour
Although
all
three
plants
considered
are
automatic
in
operation,
the
labour
requirements
differ
considerably.
With
an
ion
exchange
system,
labour
is
limited
to
monitoring
the
performance
of
an
automatic
plant
with
an
occasional
manual
intervention
to
add
more
resins
as
dictated
by
the
guarantee
(less
than
10
per
cent
resin
activity
loss
over
500
complete
cycles.
This
represents
approximately
2.2
per
cent
of
daily
running
costs).
With
electrodialysis
however,
in
addition
to
plant
mon-
itoring,
periodic
stack
dismantling
and
checking
mem-
branes/spacer
condition
is
required.
The
time
required
depends
to
some
extent
on
the
demineralization
level
being
attempted
but
up
to
40
man
hours/week
may
be
required
for
a
plant
performing
90
per
cent
demineralization
of
227,000
1/d
raw
whey
equivalent.
Energy
cost
sensitivity
As
energy
costs
escalate
the
importance
of
assessing
the
process
sensitivity
to
increasing
energy
costs
becomes
more
critical.
Electrodialysis
utilizes
some
40-50
times
as
much
electrical
power
as
ion
exchange
and
we
would
suspect
electrodialysis
to
be
much
more
sensitive
to
this
consider-
ation
than
ion
exchange.
I
believe
this
to
be
offset
by
the
fact
that
increased
energy
costs
result
in
increased
chemical
costs
and
increased
transport
charges.
On
balance
I
would
suggest
that
the
effect
of
increased
energy
costs
on
the
cost
of
chemicals
in
the
case
of
ion
exchange
marginally
outweighs
the
increased
cost
of
direct
electrical
energy
used
in
electrodialysis
although
this
is
not
an
easy
matter
to
evaluate.
48
Journal
of
the
Society
of
Dairy
Technology,
Vol.
33,
No.
2,
April
1980
12
11
10
-
c;
9
E
7
cri
_sr
1
2;
6
0
g
5
rn
4
0
8
Salt
disposal
The
disposal
of
the
extracted
ash
content
from
whey
is
a
problem
common
to
both
ion
exchange
and
electrodialysis.
However,
the
reagents
used
to
regenerate
the
ion
exchange
resins
are
only
partly
offset
by
the
chemicals
used
in
the
electrodialysis
system.
A
salt
balance
for
both
ion
exchange
and
electrodialysis
is
presented
in
Table
1.
The
water
volume
from
the
demineralizing
plant
is
only
a
part
of
any
factory
effluent
and
overall
the
salt
content
shown
above
will
be
effectively
diluted.
Nevertheless,
in
any
plant
feasibility
evaluation
this
is
one
of
the
major
factors
to
be
considered
in
plant
siting.
Product
analyses
I
have
not
considered
the
detailed
analysis
of
the
products
produced
by
ion
exchange
and
electrodialysis
as
I
under-
stand
this
will
be
covered
in
depth
by
other
speakers
at
this
Symposium,
and
is
an
extensive
subject
in
its
own
right.
Yield
The
process
costings
presented
here
are
very
much
de-
pendent
on
overall
plant
yield
and
a
summary
of
these
figures
as
claimed
by
the
manufacturers
of
the
various
systems
is
presented
in
Table
2
and
Figure
8.
TABLE
2
Relative
plant
overall
yield
%Overall
yield
Relative
yield/1,000
kg
TABLE
3
Comparison
of
variables
related
to
potential
versus
material
leaching
Typical
90%
Effective
operating
demineralizing
maximum
temperature
contact
time
diffusion
°C
distance
Electrodialysis
30-45
Up
to
6
h*
0.3
mm
Ion
exchange
8-12
20-25
min
0.2-0.4
mm
*SRTI
claim
short
batches
of
20
minutes
for
50
per
cent
demineralizing.
foods.
Partly
I
consider
this
to
be
an
historical
situation
in
which
the
initial
screening
and
product
acceptability
trials
were
conducted
using
electrodialyzed
whey
powder.
Given
the
same
materials
in
membrane
form
or
resin
form
the
main
factors
involved
in
leaching
any
residual
monomer
would
be
temperature
of
operation,
product
contact
time
and
monomer
diffusion
distance.
As
Table
3
shows,
the
operating
temperature
and
contact
time
are
both
lower
for
ion
exchange
while
the
effective
maximum
diffusion
distance
is
similar
for
both
processes.
On
this
basis
I
suggest
that
ion
exchange
is
no
more
likely
to
produce
potentially
leachable
components
in
any
product
than
electrodialysis.
50%
90%
50%
90%
Demin
Demin
Demin
Demin
Applexion
(I.E.)
95
90+
1,000
kg
1,000
kg
SRTI
(E.D.)
90-92
83-86
947-968
kg
922-956
kg
Ionics
(E.D.)
90
75-80
947
kg
833-889
kg
Yield
is
defined
in
the
above
as
(kg
dry
matter
out\
kg
dry
matter
in
/
100
90
1-4-
80
E
a,
V
,
5
70
0
60
50
Applexion
SRTI
Ionics
60
70
80
90
100
Extent
of
demineralization,%
Fig.
8.
Graph
of
yield
versus
demineralization
level
Product
acceptability
The
use
of
resins
in
the
treatment
of
foods
for
human
con-
sumption
has
been
portrayed
as
a
potential
problem
due
to
possible
leaching
of
monomer
from
the
resin
beads.
Electrodialysis
membranes,
however,
are
made
from
almost
identical
materials
as
ion
exchange
resins,
but
have
been
used
successfully
for
some
considerable
time
in
the
sen-
sitive
area
of
demineralizing
whey
destined
for
use
in
baby
Electrodialysis
and
ion
exchange
Scale
:
227000
litreiday
Ionics
SRTI
Applexion
2
90
95
Fig.
9.
Graph
showing
overall
plant
economics
Costings
The
basis
of
costing
used
in
this
presentation
is
outlined
in
detail
in
Appendices
1,
2
and
3.
Each
of
the
plants
con-
sists
of
an
automatic
plant,
delivered
complete
to
site
in
the
United
Kingdom,
including
an
estimate
for
erection
and
commissioning.
Included
is
CIP
capability;
in
the
case
of
the
ion
exchange
system
only
(although
some
of
these
components
would
also
be
necessary
for
electrodialysis),
bulk
chemical
storage
tanks,
transfer
pumps
and
water
recovery
tanks
and
pumps
have
been
included
(see
Fig.
9).
0
50
60
70
80
Demineralizing
,
%
Journal
of
the
Society
of
Dairy
Technology,
Vol.
33,
No.
2,
April
1980
49
APPENDIX
1
Costing
basis:
as
at
1st
October,
1979
2.5
p/kWh
Mains
13
p/m
3
Condensate
(if
available)-Free
10
year
straight
line
250
operating
days/year
(Delivered
18
ton
loads)
Sodium
hydroxide
10.6
p/kg
(100
%)
Hydrochloric
acid
13.4
p/kg
(100%)
Sulphuric
acid
4.4
p/kg
(100
%)
Cationic
-
76p/I
Anionic
-
£2.72/1
£3.50/man
hour
including
supervision
element
2%/year
of
capital
cost
1979/80
Mogden
Formula
for
S.E.
England
Unit
charge-4.22+
Ot.3.48
St.2.84
P/m
3
300
365
Where
Ot
-BOD
of
average
effluent
stream
in
mg/1
after
one
hour
settlement
and
St
-The
total
suspended
solids
in
mg/I
at
pH
7
0.55
p/kg
steam
at
120
lb/in
2
(£2.50/1,000
lb
steam)
2.4
p/M
Cal.
with
chilled
water
(£6.00/M
Btu)
As
per
manufacturers
recommendation
$2.16
£1
-00
9
.2FF
£1
BO
No
account
has
been
taken
of
any
import
duties
in
this
evaluation
50,000
igal/day
Protein
0.7
Lactose
4.7
Ash
0.6%
Fat
0.1%
Lactic
acid
0.2
%
Total
solids
6.3
1.
Power:
2.
Water:
3.
Capital
depreciation:
4.
Chemicals:
5.
Resins:
6.
Labour:
7.
Maintenance:
8.
BOD
treatment:
9.
Steam:
10.
Cooling:
11.
Membrane
and
other
spares:
12.
Exchange
rate
assumed
13.
Plant
size:
14.
Whey
composition:
APPENDIX
2
Plant
supply
list
Applexion
ion
exchange
SRTI
electrodialysis
Ionics
electrodialysis
Resin
columns
Associated
pipework
Associated
automatic
valves
Resins
Water
recovery
tanks
Water
recovery
pumps
Bulk
chemical
storage
tanks
Chemical
transfer
pumps
CIP
system
(integral)
Delivery
to
UK
site
Erection
Commissioning
Electrodialysis
stacks
Associated
pipework
Associated
automatic
valves
Membranes/spacers
CIP
system
Delivery
to
UK
site
Erection
Commissioning
Electrodialysis
stacks
Associated
pipework
Associated
automatic
valves
Membranes/spacers
CIP
system
Delivery
to
UK
site
Erection
Commissioning
Although
50
and
90
per
cent
demineralizing
have
been
used
as
the
main
comparison
points
in
these
costings,
ion
exchange
conventionally
achieves
94-95.
per
cent
deminer-
alizing
and
can
achieve
98
per
cent
if
required.
To
obtain
90
per
cent
from
94
per
cent
demineralized
material
in-
volves
dilution
with
undemineralized
whey
to
the
extent
of
4-5
per
cent
and
this
would
appear
as
additional
pro-
duction
volume.
For
these
costings,
the
advantages
this
brings
have
not
been
considered.
The
Mogden
Formula
1978/79
as
defined
in
Appendix
1
has
been
used
to
calculate
biochemical
oxygen
demand
(BOD)
discharge
costs.
This
is
to
a
major
extent
influenced
by
the
process
yield,
and
it
may
not
be
the
best
indicator
for
effluent
costing,
however,
I
know
of
no
other
widely
used
assessment
method
which
could
be
objectively
applied
in
the
United
Kingdom.
As
stated
initially,
it
is
very
difficult
to
obtain
exact
equivalence
in
comparing
processes
and
one
point
which
influences
the
Ionics
costings
adversely
is
the
time
of
oper-
ation
per
day
for
the
90
per
cent
demineralized
case.
This
is
set
at
14
h/d
and
in
effect
means
that
the
plant,
if
operat-
ing
for
18
h/d,
could
produce
an
additional
25-30
per
cent
product.
The
economics
of
the
Ionics
plant
at
high
de-
mineralization
would
be
much
better,
had
a
plant
of
say
60,000
gal/d
(270,000
1/day)
been
chosen
for
this
comparison.
In
assessing
the
total
dry
matter
produced
per
day,
I
have
taken
the
higher
yield
figures
offered
by
Ionics
and
SRTI
and
these
figures
reflect
recent
results
from
their
newest
plants.
It
must
again
be
emphasized
that
these
costings
are
gen-
eralized
only
and
a
specific
project
would
have
to
take
into
account
the
conditions
and
costs
local
to
any
projected
plant.
CONCLUSIONS
1.
The
capital
cost
for
an
ion
exchange
demineralization
system,
even
including
additional
peripheral
equipment,
is
considerably
less
than
electrodialysis,
especially
so
at
high
levels
of
demineralization.
2.
The
overall
yield
with
ion
exchange
is
better
and
the
operating
costs
lower
than
with
electrodialysis,
this
being
more
pronounced
as
the
demineralization
level
increases.
3.
The
salt
disposal
problem
with
ion
exchange
is
signifi-
cantly
greater
than
with
electrodialysis
and
may
influ-
ence
the
siting
of
new
plants.
4.
Historically,
formulators
of
baby
foods
have
tended
to
employ
electrodialysis
as
a
means
of
demineralizing
whey,
but
in
view
of
the
capital
and
running
economics
to
be
made
with
ion
exchange
at
high
demineralizing
levels
and
the
similarity
of
the
materials
employed
in
both
processes,
there
is
increasing
pressure
now
to
change.
5.
For
very
high
demineralizing
levels,
over
90
per
cent,
the
only
practicable
commercially
developed
method
is
ion
exchange.
50
Journal
of
the
Society
of
Dairy
Technology,
Vol.
33,
No.
2,
April
1980