Humic acid fouling during microfiltration

A major factor limiting the use of microfiltration for surface water treatm ent is membrane fouling by natural organic matter. The extent and mechanism s of humic acid fouling during microfiltration have been examined using sti rred cell filtration experiments and scanning electron microscopy. The exte nt of fouling was strongly dependent on both the source and preparation of the humic acid solutions. The large flux decline observed during constant p ressure microfiltration was caused by the formation of a humic acid deposit located on the upper surface of the membrane. Prefiltration of the humic a cid solutions dramatically reduced the rate of fouling through the removal of large humic acid aggregates. The initial fouling in this system was dete rmined almost entirely by the convective deposition of these large particle s/aggregates on the membrane surface. This initial deposit accelerated the subsequent rate of humic acid fouling, possibly serving as a nucleation sit e for deposition of macromolecular humic acids. (C) 1999 Elsevier Science B .V. All rights reserved.