Fouling of Microfiltration and Ultrafiltration Membranes by Natural Waters

Abstract

Membrane filtration (microfiltration and ultrafiltration) has become an accepted process for drinking water treatment, but membrane fouling remains a significant problem. The objective of this study was to systematically investigate the mechanisms and components in natural waters that contribute to fouling. Natural waters from five sources were filtered in a benchtop filtration system. A sequential filtration process was used in most experiments. The first filtration steps removed specific components from the water, and the latter filtration steps investigated membrane fouling by the remaining components. Particulate matter (larger than 0.45 microm) was relatively unimportant in fouling as compared to dissolved matter. Very small colloids, ranging from about 3-20 nm in diameter, appeared to be important membrane foulants based on this experimental protocol. The colloidal foulants included both inorganic and organic matter, but the greatest fraction of material was organic. When the colloidal fraction of material was removed, the remaining dissolved organic matter (DOM), which was smaller than about 3 nm and included about 85-90% of the total DOM, caused very little fouling. Thus, although other studies have identified DOM as a major foulant during filtration of natural waters, this work shows that a small fraction of DOM may be responsible for fouling. Adsorption was demonstrated to be an important mechanism for fouling by colloids.

Effect of NOM characteristics and membrane type on microfiltration performance

“…A small component of the total NOM was also found to be responsible for the major fouling of MF membranes in another study (Howe and Clarke 2002). NOM in natural water samples was fractionated with UF membranes to obtain various MW fractions.…”

Enhanced ultrafiltration PES membranes doped with mesostructured functionalized silica particles

“…However, because of the hydrophobic nature of most polymers used for UF membrane preparation, these filtration materials are susceptible to organic fouling due to the adsorption or deposition of retained organic compounds [3,4]. In this regard, polyethersulfone (PES) appears quite suitable for this application due to its high chemical and thermal stabilities, good oxidation resistance and excellent mechanical properties [5].…”

Hydraulically irreversible fouling on ceramic MF/UF membranes: Comparison of fouling indices, foulant composition and irreversible pore narrowing

“…Tian et al and Kimura et al observed correlation between biopolymers and the fouling in both UF [20] and MF [21] membranes. Moreover, Howe and Clark [24] found that the organic matter and particles in natural water ranging from 3 nm to 14 nm in size predominately contribute to the fouling of MF and UF membranes. The inorganic particles in the nanometre and micrometre range, existing in natural surface water, also exacerbate the membrane fouling by hindering the back diffusion of organic matter from the membrane surface [25,26].…”