The primary goal of this AwwaRF funded research included the following: contrast natural organic matter (NOM)-related fouling
potential for different types of waters (allochthonous versus autochthonous); and, relate observed
fouling to membrane properties and understand fouling observed through state-of-the-art membrane
autopsy techniques. Interactions between water quality, pretreatment chemicals, membrane
materials, and membrane configurations were tested at pilot-scale under various operating
conditions. Pilot studies were conducted at two locations: the Tampa WTP, FL (predominantly
allochthonous NOM) utilizing Zenon's immersed membranes; and, at the White River WTP, IN
(predominantly autochthonous NOM), using U.S. Filter's CMF-L pilot unit, utilizing raw,
coagulated and clarified waters as feed. The pilot testing program was designed to distinguish
between three types of NOM-based fouling, including the following: hydraulically reversible fouling; chemically reversible
fouling; and, irreversible fouling. Autopsy tools included: contact angle; field emission
scanning electron microscopy (FESEM); providing a visualization of foulant deposition;
Fourier transform infrared spectroscopy (FTIR); pyrolysis GC/MS of extracted foulant; and,
elemental (C and N) composition of extracted foulant. As a general rule, there were only small
changes in contact angle before and after fouling. With more severely fouled membranes, contact
angle slightly increased for a hydrophobic membrane and either an autochthonous or an
allochthonous NOM source. FESEM images were made of both the external and internal surfaces
of the fibers autopsied after fouling. For both the allochthonous and autochthonous sources, a
deposit was observed at the inner surface of the fibers, with material possibly corresponding to
microbial entities (algae or/and bacteria), particularly for the autochthonous source where algae
were observed during the period of testing. Most of the FTIR spectra of extracted foulant indicated
the presence of organic matter derived from bacterial origin (aminosugars, proteins, lipids). All of
the pyrolysis GC/MS chromatograms of extracted foulant showed strong indicators of the presence
of natural biopolymers with the presence of peaks that are produced from the thermal degradation
of proteins, sugars, aminosugars, and lignin-type structures. The autopsy results were generally
supportive of the findings related to feed-water NOM composition in which autochthonous NOM
characteristics were found to correspond to a higher fouling potential. Includes 10 references, tables, figures.
| Edition : | Vol. - No. |
| File Size : | 1
file
, 2.4 MB |
| Note : | This product is unavailable in Ukraine, Russia, Belarus |
| Number of Pages : | 53 |
| Published : | 11/01/2008 |
