61
SECTION 5,
continued
5.7
Making BOD Determinations
Use the Hach BOD Accessory Kit with a magnetic stir plate and a
standard 300-mL BOD bottle.
1. Fill a standard 300-mL BOD bottle with the water sample and
insert the overflow funnel.
2. Insert the DO probe into the funnel and bottle.
3. Place the BOD bottle on a magnetic stirrer so that the probe is
over the center of the stir plate.
4. Start the magnetic stirrer and increase the speed until the
rotor loses its cycle. Adjust until the rotor regains its cycle
and mark this point on the speed scale of the stirrer. This
identifies the optimum working point. Insufficient stirring
will cause erroneously low readings.
Note: If air bubbles develop below or on the probe membrane, allow the
stirrer about five seconds to remove them, or hold the probe at a
slight angle and tap gently.
5.8
Measuring Dissolved Oxygen in Water (0 to 20 mg/L)
1.
Assemble the
dissolved oxygen probe
as described in
Section 5.3.1 on
page 50.
2.
At least thirty
minutes before
measurement, polarize
the probe by connecting
it to the meter. See
Section 5.4.1 on
page 52.
3.
Zero the
sens
ion
156 Dissolved
Oxygen meter if
measuring DO levels
less than 1 mg/L or 10%
saturation.
4.
Secure the probe
cable to the calibration
and storage chamber.
exit
READ
READ
enter
conc %
5
setup
CE
1
time
3
light
2
6
erase
9
recall
7
store
8
cal
0
4
review
.
sens
ion6
Dissolved O
2
enter
exit
7 8 9
4 5 6
1 2 3
enter
exit
C
Stabilizing...
