The objective of this project is to determine the role of colloid particle size and stability on performance of membranes used in water and wastewater treatment process. While models for particle transport in membrane modules have been developed which treat transport mechanisms individually, no model has yet been proposed which combines these mechanisms nor has the interaction between these mechanisms been evaluated experimentally to produce an complete picture of the conditions under which colloids may reduce the flux across membranes. Particle transport by Brownian diffusion, shear-induced, and lateral migration in a flat plate membrane module will be studies using pressure field-flow fractionation techniques. By this method, a pulse of particles is introduced at the inlet to a porous channel. The particle concentration response in the outlet of this idealized membrane module is monitored over time using UV absorbance and checked against electrical sensing zone and photon correlation measurements. The retention time of particles in the channel can be compared with the retention time calculated assuming a single mode of back-transport. Particle size and permeation rate through the membrane will be varied to produce conditions that favor transport by each of these mechanisms. The effect of electrokinetic interactions on back-transport will be evaluated by performing identical experiments with charged and uncharged particles. The proposal leading to this award was submitted in response to NSF 88-99, Research Initiation Awards. The proposed work may lead to improvements in the Engineering design of membrane and process using membranes for treatment of water and wastewater used industrially and municipally.
