(342b) Re-Examining the Fundamental Fouling Equations

Fouling can be characterised as being due to one or more of adsorption, cake formation or pore blocking. These modes lead to different rates of blockage or partial blockage of the active membrane area or to deposition of a layer onto the membrane surface. Generally, following Hermia (1982), four fouling mechanisms for porous membranes have been hypothesized: (i) complete pore blocking; (ii) internal pore blocking; (iii)partial pore blocking; and (iv)cake filtration. The original equations were for dead-end filtration. Due allowance for crossflow has been made, e.g. by Field et al (1995). However these models assume that the removal term is a function of shear rate alone. This paper will re-examine the removal term and propose alternatives based upon particle-release conditions. The removal term is hypothesized as being proportional to shear rate and inversely proportional to flux. In so doing, Kuiper et al's (2000) work is generalised and a complete set of alternative equations to those developed previously is obtained. This new set will be compared with existing equations.

R.W. Field, D. Wu, J.A. Howell, B.B. Gupta, (1995) Critical flux concept for microfiltration fouling. J. Membr. Sci. 100: 259?272.

J. Hermia, (1982) Constant pressure blocking filtration laws -Application to power-law non-Newtonian fluids, Trans.IChemE 60: 183-187.

S. Kuiper, , C. J. M. van Rijn, W. Nijdam, G. J. M. Krijnen and M. C. Elwenspoek (2000) Determination of particle-release conditions in microfiltration: a simple single-particle model tested on a model membrane J. Membr. Sci. 180: 15-28