Abstract
Two types of submerged membrane bioreactors (MBR): hollow fiber (HF) and
hollow sheet (HS), have been studied and compared in terms of energy
consumption and average shear stress over the membrane wall. The analysis
of energy consumption was made using the correlation to determine the
blower power and the blower power demand per unit of permeate volume.
Results showed that for the system geometries considered, in terms the of
the blower power, the HF MBR requires less power compared to HS MBR.
However, in terms of blower power per unit of permeate volume, the HS MBR
requires less energy. The analysis of shear stress over the membrane
surface was made using computational fluid dynamics (CFD) modelling.
Experimental measurements for the HF MBR were compared with the CFD model
and an error less that 8% was obtained. For the HS MBR, experimental
measurements of velocity profiles were made and an error of 11% was found.
This work uses an empirical relationship to determine the shear stress
based on the ratio of aeration blower power to tank volume. This
relationship is used in bubble column reactors and it is extrapolate to
determine shear stress on MBR systems. This relationship proved to be
overestimated by 28% compared to experimental measurements and CFD
results. Therefore, a corrective factor is included in the relationship in
order to account for the membrane placed inside the bioreactor.
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