Environmental Engineering Reference
In-Depth Information
Fig. 6.12
DO and ORP measurements in Biofilm: (
a
) schematic diagram of experimental setup
(
1
. video display;
2
. data acquisition system;
3
. 3-D micromanipulator;
4
.MEorMEA;
5
.
charge-coupled device (CCD) camera;
6
. stereomicroscope;
7
. open-channel chamber;
8
.vibra-
tion isolation table;
9
. Faraday cage;
10
. peristaltic pump;
11
. feed tank; and
12
. oxygen cylinder),
(
b
) photograph of the experimental setup, (
c
) microprofiles of dissolved oxygen (DO,
)and
oxidation-reduction potential (ORP,
) in biofilm. Filled shapes represent microprofiles with the
MEA (one sensor of each type) and empty shapes represent microprofiles with the ME. The data
is the average of six measurements, and (
d
) DO microprofile recorded with the MEA during the
biofilm insertion (
•◦
•
) and withdrawal (
◦
). The data is the average of six measurements. From [58]
(0.5%) was added as a supplemental oxygen source to maintain 5.0
±
0.5 mg/L DO
in the reactor.
Biofilm microprofile measurements.
Figure 6.12b shows the experiment setup for
the microprofile measurements inside the biofilm [58]. Multispecies biofilm grown
on slides were taken from the closed reactor and placed in the open channel test
chamber to obtain oxygen and redox potential profiles. The open channel chamber
(7.85 cm L, 2.9 cm W, 1.2 cm H) was mounted under a stereo microscope with a
charge-coupled device (CCD) camera (Model JE-3662 HR, Javelin Elec., Torrance,
CA) situated on a Micro-g series high-performance vibration isolation table (63-
527-01, TMC, Peabody, MA) inside a Faraday cage (TMC, MA). Feed solution with
the same composition as in the closed biofilm reactor was continually aerated and
recycled (2.35 mL/min) through the open channel chamber with a peristaltic pump
mounted outside of the Faraday cage. The biofilm sample was placed in the chamber
for at least 30 min before performing measurements. Microelectrodes were mounted
and positioned using a motor-driven 3-D micromanipulator (Model 11N, Narisige,
Japan). Oxygen profiles were measured at 10-50
μ
m intervals into the biofilm; ORP
