AWWA ACE56156

The keys to unlocking many of the causes of membrane fouling can come directly from close evaluation of the membrane surface itself. Deposits, which accumulate on the surface of the membrane, can be used in their own identification. The location and concentration of these deposits can lead to an understanding of the hydrodynamics through the spiral-wound element and the feed water spacer. As part of a quantitative research study, twelve DL4040C (4. diameter x 40. length) spiralwound membrane elements manufactured by Osmonics DESAL were dissected and examined to determine what surface patterns may be characteristic of natural organic matter (NOM) and particle fouling. Experiments were conducted with waters that had been spiked with concentrated NOM and particles. Four NOM concentrations (i.e., 0, 5, 15, and 25 mg/L as total organic carbon or TOC) and three particle size ranges (i.e., no added ancillary particles, 0.5-1.0 um particles, and >1.0 um particles) were tested resulting in a total of 12 experiments. Each experiment was conducted with a new spiral wound element, which was dissected immediately following testing. Two types of membrane surface evaluations were performed: visual and microscopic. Visual evaluations were performed by scanning cut sections of membrane leafs (8.5 x 11 inches) directly into the computer using a flatbed scanner. Images were enhanced and magnified using Adobe PhotoShop. Microscopic evaluations were performed on specimens cut from membrane leafs and viewed under a scanning electron microscope (SEM). In conjunction with the SEM, energy dispersive spectrometry was used to generate spectra to confirm NOM deposits as well as identify mineral deposits. For clarity, SEM micrographs were inserted into each respective spectrum as a point of reference. Includes 2 references, figures.

Product Details

Edition:

Vol. - No.

Published:

06/16/2002

Number of Pages:

11

File Size:

1 file , 4.5 MB