Effect of membrane configuration on bench-scale MF and UF fouling experiments.

Hollow fiber and flat sheet membranes were compared in side-by-side bench-scale experiments to evaluate whether the configuration has an impact on the rate of membrane fouling. Both microfiltration (MF) and ultrafiltration (UF) membranes were evaluated. In general, flat sheet membranes fouled more rapidly than hollow fiber membranes. Pretreatment such as coagulation generally affected both configurations similarly, but in some cases coagulation reduced fouling on hollow fiber membranes but increased fouling on flat sheet membranes. Prefiltration to remove foulants above 1microm in size had a consistent effect on both configurations. A bench-scale apparatus employing a single-fiber module that allows testing over multiple filter runs with integral backwashing capabilities was demonstrated to provide more detailed information about fouling, which can be applied to full-scale applications. When bench-scale tests are to be used to screen treatment options for full-scale applications, the use of a backwashable hollow fiber system is recommended.

Effect of coagulation on the size of MF and UF membrane foulants.

Microfiltration (MF) and ultrafiltration (UF) have become common water treatment technologies for the removal of particles from natural waters. Many water utilities are now integrating MF/UF with other treatment processes to provide treatment for nonparticulate contaminants. Research is needed to understand the impact that other processes have on MF/UF performance. This study was conducted to investigate the interactions between water quality, coagulation, and membrane fouling. The study examined the fouling of MF/UF membranes by natural waters with and without coagulation by specific fractions of constituents in natural water, separated by size. This research found thatthe component of natural organic matter (NOM) smaller than 100 kDa contributes relatively little to fouling during filtration of either raw or coagulated water. The fraction between 1 microm and 100 kDa contributes a significant portion of the fouling. After coagulation pretreatment, fouling due to various size fractions in the feedwater can change.