Characterization of membrane foulants in drinking water treatment

Membranes are very effective in removing a wide variety of water contaminants. Therefore, the use of these processes in water purification to replace or to improve conventional treatment has increased. An inherent problem of membranes is fouling, the accumulation of materials (foulants) near, on, or within the membrane that causes a reduction in the amount of product water over time. As a result of fouling, capital and operating costs of membrane systems are higher, making them less attractive. In this project the effect that several operating conditions have on the characteristics of the foulant layer is evaluated. The tested operating conditions included biofiltration pretreatment and permeate flux. Commercial low-pressure membranes were employed and characterized according to their physicochemical properties before and after being fouled with organic matter-rich feed solutions. The foulant layer was analyzed in terms of its chemical and microbiological characteristics, aided by microscopic images (scanning electron microscopy, SENT and atomic force microscopy, AFM). Since the commercial membrane employed in this study was a loose UF membrane, most of the material encountered in the foulant layer was in particulate form. Pretreatment decreased the amount of organics and microorganisms deposited on the membrane. However, similar microbial species were found in the foulant layer of membranes with and without pretreatment.