| The use of membranes to treat effluents from the pulp and paper industry has been evaluated. Four applications related to the treatment and recycling of effluents were tested, and two were selected as having good industrial applicability: (1) microfiltration of old newsprint de-inking effluent containing flexographic ink; (2) treatment of an effluent from a mill using recycled old corrugated containers using a membrane bio-reactor.; The membrane system adopted in this research has a unique configuration. It consists of a bundle of hollow-fiber microfiltration membranes submerged in a tank into which the effluent is introduced. Vacuum is used inside the fiber lumen to create transmembrane pressure differential, and aeration to promote high-shear stress at the membrane surface to minimize concentration polarization and fouling. Periodic reverse filtration (backflushing) is also used.; A semi-empirical model to predict the permeate flux for this membrane configuration has been developed. The model was based on Darcy's law combined with a particle mass balance equation, and assumes that non-diffusive transport phenomena are the main mechanisms for the back-transport of particles from the membrane surface to the bulk solution during filtration. The model incorporates the use of reverse filtration.; The model has been validated by laboratory experiments using six different suspensions: flexographic ink (phib = 0.005 and 0.01); calcined alumina (phib = 0.02 and 0.03); and yeast (phib = 0.01 and 0.02), where phi b is the solid volume fraction in the suspension. The results showed good agreement between model prediction and experimental observations. |
