AWWA ACE69046

The primary goal of this AwwaRF funded research included the following: contrast natural organic matter (NOM)-related foulingpotential for different types of waters (allochthonous versus autochthonous); and, relate observedfouling to membrane properties and understand fouling observed through state-of-the-art membraneautopsy techniques. Interactions between water quality, pretreatment chemicals, membranematerials, and membrane configurations were tested at pilot-scale under various operatingconditions. Pilot studies were conducted at two locations: the Tampa WTP, FL (predominantlyallochthonous 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 distinguishbetween three types of NOM-based fouling, including the following: hydraulically reversible fouling; chemically reversiblefouling; and, irreversible fouling. Autopsy tools included: contact angle; field emissionscanning 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 smallchanges in contact angle before and after fouling. With more severely fouled membranes, contactangle slightly increased for a hydrophobic membrane and either an autochthonous or anallochthonous NOM source. FESEM images were made of both the external and internal surfacesof the fibers autopsied after fouling. For both the allochthonous and autochthonous sources, adeposit was observed at the inner surface of the fibers, with material possibly corresponding tomicrobial entities (algae or/and bacteria), particularly for the autochthonous source where algaewere observed during the period of testing. Most of the FTIR spectra of extracted foulant indicatedthe presence of organic matter derived from bacterial origin (aminosugars, proteins, lipids). All ofthe pyrolysis GC/MS chromatograms of extracted foulant showed strong indicators of the presenceof natural biopolymers with the presence of peaks that are produced from the thermal degradationof proteins, sugars, aminosugars, and lignin-type structures. The autopsy results were generallysupportive of the findings related to feed-water NOM composition in which autochthonous NOMcharacteristics were found to correspond to a higher fouling potential. Includes 10 references, tables, figures.

Product Details

Edition:

Vol. - No.

Published:

11/01/2008

Number of Pages:

53

File Size:

1 file , 2.4 MB