A transient biological fouling model for constant flux microfiltration
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abstract
Microfiltration technology is a widely used engineering strategy for fresh water production and water treatment. The major concern in many applications is the formation of a biological fouling layer leading to increased hydraulic resistance and flux decline during membrane operations. The growth of bacteria constituting such a biological layer implicates the formation of a multispecies biofilm and the consequent increase of operational costs for reactor management and cleaning procedures. To predict the biofilm growth and evolution during the filtration process, a one-dimensional continuous model has been developed by considering a free boundary value problem describing biofilm dynamics and EPS production in different operational phases of microfiltration systems. The growth of microbial species and EPS is governed by a system of hyperbolic PDEs. Substrates dynamics are modeled thorough parabolic equations accounting for diffusive and advective fluxes generated during the filtration process. The free boundary evolution depends on both microbial growth and detachment processes. The proposed model has been solved numerically to simulate biofilm evolution during biologically relevant conditions, and to investigate the hydraulic behavior of the membrane. The model has been calibrated and validated using lab scale experimental data. In all cases, numerical results accurately predicted the membrane pressure drop occurring in the microfiltration system.
