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Improved oxygen mass transfer model for pulsed gas injection in bubble column based on population balances of the dispersed gas phase
Art der Abschlussarbeit
Master
Autoren
- Oleshova, Mariia
Betreuer
- Prof. Dr. André Lerch
- M.Sc. Sibel Tas-Köhler
Weitere Betreuer
Dr. Sebastian Reinecke (HZDR), Dipl.-Ing. Robert Herrmann-Heber (HZDR)
Abstract
In biological wastewater treatment, the aeration process disperses air into the liquid
phase in the form of air bubbles. It provides an anaerobic environment for microbial
degradation of organic matter. However, aeration is also the most energy-consuming
and cost-generating step which corresponds to 50 - 80 % of the total wastewater treatment
plant (WWTP) energy budget and to about 1 % of total electricity consumption
in developed countries. One way to achieve aeration energy-optimization is the implementation
of intermittent gas injection. Therefore, the main objective of this thesis was
to investigate the effect of pulsed aeration on the oxygen mass transfer. Experiments
were performed with the help of an optical flow microscope in order to study bubble
size distribution (BSD) dynamics, bubble size, and bubble rise velocity while the measurements
of oxygen mass transfer coefficient obtained with the use of dissolved oxygen
sensors. The overall volumetric oxygen transfer coefficient was calculated according
to Higbie penetration theory. Local and global oxygen transfer coefficient were found and compared to
values measured by a traditional gassing-out method. Based on the experimental BSD
the population balance model (PBM) was formulated, calibrated, and then solved in
MATLAB software. It was shown that the PBM can predict the BSD dynamics along
the height of the column operated under different operating conditions. The Higbie
oxygen mass transfer theory considers the single value of the Sauter mean diameter for
the entire column. In this work, the modeling approach that takes into account the
local BSD was implemented in order to calculate the oxygen transfer coefficient.
phase in the form of air bubbles. It provides an anaerobic environment for microbial
degradation of organic matter. However, aeration is also the most energy-consuming
and cost-generating step which corresponds to 50 - 80 % of the total wastewater treatment
plant (WWTP) energy budget and to about 1 % of total electricity consumption
in developed countries. One way to achieve aeration energy-optimization is the implementation
of intermittent gas injection. Therefore, the main objective of this thesis was
to investigate the effect of pulsed aeration on the oxygen mass transfer. Experiments
were performed with the help of an optical flow microscope in order to study bubble
size distribution (BSD) dynamics, bubble size, and bubble rise velocity while the measurements
of oxygen mass transfer coefficient obtained with the use of dissolved oxygen
sensors. The overall volumetric oxygen transfer coefficient was calculated according
to Higbie penetration theory. Local and global oxygen transfer coefficient were found and compared to
values measured by a traditional gassing-out method. Based on the experimental BSD
the population balance model (PBM) was formulated, calibrated, and then solved in
MATLAB software. It was shown that the PBM can predict the BSD dynamics along
the height of the column operated under different operating conditions. The Higbie
oxygen mass transfer theory considers the single value of the Sauter mean diameter for
the entire column. In this work, the modeling approach that takes into account the
local BSD was implemented in order to calculate the oxygen transfer coefficient.
Zugeordnete Forschungsschwerpunkte
- Trink-, Reinst- und Prozesswasseraufbereitung
Schlagwörter
Activated sludge process, Diused aeration, Oxygen mass transfer, Bubbly ow, Population balance
Berichtsjahr
2021