Numerical simulation of bubble induced shear in membrane bioreactors: effects of mixed liquor rheology and membrane configuration

Water Research
Xuefei LiuGreg Leslie

Abstract

A CFD model, incorporating an empirically determined rheology model and a porous media model, was developed to simulate bubble induced surface shear in membrane bioreactors configured with hollow fibre membranes with outer diameters ranging from 1.3 to 2.4 mm, arranged in vertically orientated modules with packing density from 200 to 560 m(2)/m(3). The rheology model was developed for mixed liquor suspended solids (MLSS) concentrations of 3 to 16 gL(-1) in the presence and absence of coagulant (generated by addition of a ferrous salt) for shear rates ranging from 0 to 500 s(-1). Experimentally determined particle relaxation times for the biological flocs in the mixed liquor, both in the absence and presence of iron, were negligible, consistent with an environment where positive buoyancy forces were greater than negative settling forces thereby allowing the sludge mixture to be modelled as a single continuous phase. The non-Newtonian behaviour of the mixed liquor was incorporated into the CFD simulations using an Ostwald-de Waele rheology model. Interactions between mixed liquor and hollow fibre membranes of different fibre size and packing density were described using a porous media model that was calibrated by empirical measur...Continue Reading

References

Mar 6, 2003·Bioresource Technology·Sarah PhilipsWilly Verstraete
Apr 11, 2008·Water Science and Technology : a Journal of the International Association on Water Pollution Research·J Saalbach, M Hunze
Apr 22, 2009·Water Science and Technology : a Journal of the International Association on Water Pollution Research·I Mishima, J Nakajima
Jun 19, 2012·Bioresource Technology·Lutz BöhmMatthias Kraume
Dec 12, 2012·Water Research·N RatkovichT R Bentzen

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