ESEL Paper Review_201307 24
By Hong Guo
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1, Title and Author
Title: Detailed spatio-temporal solids concentration profiling during batch settling of activated sludge using a radio racer.
Journal: Water Research
Jeriffa De Cleerca,*, Filip Jacbosb, David J. Kinnearc, Ingamar Nopensc, Rudi A. Dierckxb, Jacques Defrancqa, Peter A. Vanrolleghemc.
a Department of Chemical engineering and Technical chemistry, Ghent University, Tehcnologiepark 914,9054 Zwijnaarde, Belgium
b Department of Nuclear Medicine, Ghent University Hospital, De Pintelaan 185, 9000 Gent, Belgium
c BIOMATH: Department of Applied Mathematics, Biometrics and Process Contrl, Ghent University, Coupure Links 653, 9000 Gent , Belgium
2. Summary of Paper
In this research, the authors utilized a radiotracer and gamma cameras to get the high time and spatial resolution solids concentration profiles during the batch settling of activated sludge in a pilot ?scale column with the a height of 1m.
? Preliminary experiments:
? Preliminary experiments were needed to gain more insight in the proposed measurement technique and to answer the following questions
? Does Tc-99m Sestamibi adsorb on the sludge?
? Does Tc-99m Sestamibi change the settling properties?
? It can be concluded that the settling properties do not change with the addition of the radiotracer.
? The settling properties once again did not change with the addition of the radiotracer.
? The use of the radiotracer and measuring the radiation with a gamma camera, can be used to determine a higher solution solids concentration profile during batch settling with good accuracy.
? Pilot-scale batch settling experiments:
? The solids concentration profiles during batch settling are shown in Fig. 5 for the Destelbergen sludge and in Fig. 6 for the Deinze sludge. All profiles show the same trend. Initially the solids concentration is uniform. Subsequent profiles show the
accumulation of sludge at the base as a result of settling, as well as the decrease of the sludge blanket height.
? The concentrations at the base are continuously increasing and higher concentrations move towards the sludge blanket height. When concentrations in excess of the original one reach the sludge blanket height, the sludge blanket height decreases more slowly.
? The fact that the observed equilibrium profiles show an increasing concentration towards the base, indicates that besides hindered settling, compression settling occurs too.
? The compression solids concentration (boundary between hindered and hindered compression settling) could be estimated by averaging concentrations between 1 and 15 g/l of the equilibrium profiles.
? At concentrations lower than 15 g/l, the solids do not offer considerable resistance to further settling (effective solids stress lower than 5 Pa), but for concentrations higher than 15 g/l, the solids yield more slowly with the applied pressure.
? Compression solids concentrations can be estimated from the equilibrium profiles and are between 7and 10g/l depending on the origin of the sludge and the initial solids concentration
This research studies the behavior of activated sludge and the obtained profiles are very appropriate date for future studies.
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