Environmental Engineering Reference
In-Depth Information
Fig. 6.13
Phosphate measurements in Biofilm: (
a
) schematic diagram of up-flow chamber
(adapted from [73]), (
b
) photograph of up-flow chamber, (
c
) microprofiles of phosphorus in flocs
from the EBPR process, and comparison with the phosphorus microprofiles from conventional
microelectrode (ME) and phosphate MEA, and (
d
) penetration of microelectrode through the floc
during microprofiling [60]
using a 3-D micromanipulator (Model 11 N, Narisige, Japan) controller which was
located outside the Faraday cage. A pH meter (Model 215, Denver Instruments,
Denver, CO) was used to obtain potentiometric signals (mV) and a Balance Talk
SLTM (Labtronics Inc., Guelph, Ontario, Canada) spread logger was used to record
these electrode response (mV) continuously for monitoring the phosphate response.
An Ag/AgCl milli-electrode (MI-401, Microelectrodes Inc., Bedford, MA) was
used as a reference electrode. A commercial oxygen mini-electrode (OM-4 Oxygen
sensor, Microelectrodes Inc., Bedford, MA) was used to measure the oxygen con-
centration in the up-flow chamber while monitoring phosphate in the anaerobic
phase in the EBPR process.
Phosphate Microprofile Measurements.
During the EBPR process, PAOs in the
reactor released P to increase the 3.0 mg/L of influent phosphate to 15.0 mg/L as
P at the end of the anaerobic phase, and then performed luxury uptake in the aero-
bic phase. At the end of the aerobic phase, the phosphate concentration was down to
2.0 mg/L as P. The
in situ
measurement of the phosphate MEA sensor was conducted
in the anaerobic phase where the dissolved oxygen was below 1 mg/L and thus
caused no interference on the selectivity of the phosphate. Three to five micropro-
files of each microbial floc were measured in the up-flow chamber in a Faraday cage,
