...
Grab
...
Sample
...
Turbidity
...
Testing
...
In
...
order
...
to
...
test
...
the
...
accuracy
...
of
...
the
...
turbidimeters,
...
a
...
grab
...
sample
...
method
...
has
...
been
...
developed.
...
The
...
results
...
of
...
this
...
method
...
will
...
be
...
compared
...
to
...
the
...
results
...
from
...
the
...
turbidimeters.
...
The
...
sample
...
container
...
will
...
be
...
a
...
500
...
mL
...
glass
...
beaker.
...
It
...
is
...
very
...
important
...
that
...
the
...
water
...
undergo
...
minimal
...
shear
...
when
...
entering
...
the
...
beaker
...
so
...
that
...
flocs
...
are
...
not
...
broken
...
in
...
the
...
process.
...
Therefore,
...
the
...
following
...
procedure
...
will
...
be
...
followed
...
to
...
collect
...
a
...
sample.
...
First,
...
the
...
beaker
...
will
...
be
...
gently
...
emerged
...
while
...
angled
...
downward
...
(at
...
approximately
...
30
...
degrees),
...
so
...
that
...
the
...
area
...
that
...
the
...
incoming
...
water
...
can
...
pass
...
through
...
to
...
enter
...
the
...
beaker
...
is
...
as
...
large
...
as
...
possible.
...
This
...
can
...
be
...
seen
...
in
...
Grab
...
Sample
...
Procedure
...
...
...
.
...
Then,
...
the
...
beaker
...
will
...
be
...
rotated
...
downward
...
until
...
it
...
is
...
horizontal
...
as
...
seen
...
in
...
Grab
...
Sample
...
Procedure
...
...
...
.
...
It
...
will
...
be
...
further
...
rotated
...
until
...
fully
...
submerged
...
as
...
seen
...
in
...
Grab
...
Sample
...
Procedure
...
...
...
.
...
The
...
purpose
...
of
...
steps
...
2
...
and
...
3
...
are
...
to
...
let
...
the
...
water
...
enter
...
the
...
beaker
...
without
...
allowing
...
air
...
to
...
be
...
trapped
...
in
...
the
...
beaker.
...
If
...
air
...
bubbles
...
are
...
trapped
...
in
...
the
...
beaker,
...
then
...
they
...
may
...
break
...
flocks
...
when
...
the
...
beaker
...
is
...
righted
...
and
...
they
...
escape.
...
Then
...
it
...
will
...
be
...
fully
...
submerged
...
into
...
the
...
water
...
and
...
rotated
...
so
...
that
...
the
...
beaker
...
is
...
upright
...
as
...
seen
...
in
...
Grab
...
Sample
...
Procedure
...
...
...
.
...
Then,
...
finally,
...
the
...
beaker
...
will
...
be
...
lifted
...
vertically
...
from
...
the
...
water,
...
so
...
that
...
it
...
remains
...
full.
| Wiki Markup |
|---|
{float:right|border=2px solid black|width=200px}
{anchor:Picture 1}[!Pilot Plant^GrabSample1.jpg|width=200px!|Pilot Plant^GrabSample1.jpg]
h5. Grab Sample Procedure Picture 1
{float} |
| Wiki Markup |
|---|
{float:right|border=2px solid black|width=200px}
{anchor:Picutre 2}[!Pilot Plant^GrabSample2.jpg|width=200px!|Pilot Plant^GrabSample2.jpg]
h5. Grab Sample Procedure Picture 2
{float} |
| Wiki Markup |
|---|
{float:right|border=2px solid black|width=200px}
{anchor:Picutre 3}[!Pilot Plant^GrabSample3.jpg|width=200px!|Pilot Plant^GrabSample3.jpg]
h5. Grab Sample Procedure Picture 3
{float} |
| Wiki Markup |
|---|
{float:right|border=2px solid black|width=180px} {anchor:Picutre 4}[!Pilot Plant^GrabSample4.jpg|width=150px!|Pilot Plant^GrabSample4.jpg] h5. Grab Sample Procedure Picture 4 {float} |
The
...
water
...
will
...
be
...
allowed
...
to
...
settle
...
for
...
20
...
minutes
...
to
...
approximate
...
the
...
settling
...
that
...
should
...
occur
...
in
...
the
...
tube
...
settlers.
...
The
...
length
...
of
...
time
...
that
...
the
...
water
...
should
...
be
...
allowed
...
to
...
settle
...
was
...
determined
...
in
...
the
...
following
...
way.
...
First,
...
I
...
back-calculated
...
from
...
the
...
flow
...
that
...
we
...
had
...
been
...
running
...
through
...
the
...
tube
...
settlers
...
in
...
the
...
past
...
(40mL/min)
...
to
...
find
...
the
...
critical
...
velocity,
...
Vc,
...
associated
...
with
...
that
...
flow.
...
| Include Page | ||||
|---|---|---|---|---|
|
This gives a Velocity through the settler tube, or Valpha, to be 0.1358 cm/sec,
...
or
...
117.3
...
m/day.
...
Then
...
Vup
...
was
...
determined
...
using
...
the
...
following
...
equation:
...
| Include Page | ||||
|---|---|---|---|---|
|
Vup,
...
for
...
this
...
case
...
is
...
0.1176
...
cm/s
...
or
...
101.6
...
m/day.
...
Vc
...
is
...
the
...
critical
...
velocity
...
that
...
a
...
floc
...
must
...
have
...
to
...
drop
...
to
...
the
...
bottom
...
of
...
the
...
tube
...
settler
...
and
...
settle
...
out.
...
The
...
following
...
equation
...
from
...
Weber-Shirk
...
was
...
used
...
to
...
determine
...
Vc.
...
| Include Page | ||||
|---|---|---|---|---|
|
Vc = 0.01032
...
cm/s
...
=
...
8.92
...
m/day
...
This
...
value
...
is
...
acceptable
...
because
...
it
...
is
...
below
...
the
...
threshold
...
of
...
10m/day.
...
Then,
...
the
...
time
...
that
...
the
...
water
...
in
...
the
...
beaker
...
would
...
need
...
to
...
be
...
allowed
...
to
...
settle
...
was
...
calculated
...
as
...
follows:
...
| Include Page | ||||
|---|---|---|---|---|
|
T = 12cm/(0.01032cm/s)
...
=
...
19
...
minutes
...
23
...
seconds
...
,
...
or
...
about
...
20
...
minutes.
...
Finally,
...
the
...
settled
...
water
...
turbidity
...
of
...
the
...
grab
...
samples
...
is
...
tested
...
using
...
the
...
bench
...
turbidimeter
...
in
...
the
...
CUWTP
...
lab.
...
This
...
turbidimeter
...
is
...
calibrated
...
regularly
...
by
...
CUWTP
...
staff.
...
Results
...
of
...
grab
...
sample
...
testing
...
The
...
above
...
procedure
...
was
...
performed
...
for
...
two
...
of
...
the
...
turbidimeters
...
on
...
April
...
2,
...
2008
...
to
...
test
...
if
...
the
...
tube
...
settler
...
set-up
...
was
...
functioning
...
properly.
...
The
...
following
...
were
...
the
...
results
...
from
...
this
...
test:
...
| Turbidimeter 3 | Turbidimeter 2 |
|---|---|---|
| (NTU) | (NTU) |
Turbidimeter | 40.4 | 54.2 |
Grab Test | 61.4 | 82.3 |
Grab Test % Higher than Turbidimeter | 52% | 52% |
As can be seen from this data, the grab test had a settled turbidity that was, in both tests, 52% higher than the turbidity readings from the tube settler/turbidimeter combination. This suggests that the tube settler/ turbidimeter set-up was functioning as it should be. To verify this in another way, we changed the incoming lines between the turbidimeters, and observed that the values from the different turbidimeters agreed.