Identification and characterization of foulants and scalants on NF membrane

Identification of foulants is an important concern for membrane technology to minimize membrane fouling and to optimize feed water pretreatments. Research has been performed for the development of innovative methods for characterizing NOM and the application of methods for the identification and characterization of foulants on NF membranes. Specific objectives of this research were to: (i) develop a high performance size exclusion chromatography (HPSEC) system combined with sequential on-line detectors consisting of ultraviolet (UV, SPD-10A VP Shimadzu UV detector), fluorescence (Waters 470 Scanning Fluorescence detector), and dissolved organic carbon (DOC, Modified Sievers Total Organic Carbon Analyzer 800 Turbo), (ii) demonstrate the inherent inaccuracy of UV detection over DOC detection with HPSEC to estimate NOM molecular weight (MW), permitting better representation of MW, (iii) determine organic foulants and inorganic scalants by the analyses of membranes fouled during bench-scale and pilot-scale tests, and (iv) characterize algogenic organic matter (AOM) and identify its role in NF membrane fouling. The developed HPSEC system provides quantitative and qualitative information on the specific MW components of NOM, including the proportion of DOC concentration (by DOC measurement), aromaticity (by comparison of UV and DOC measurement), and chemical properties (by URI and fluorescence measurements). It further allows classification of organic matter as specific biopolymers (e.g., fulvic-like, protein-like, and polysaccharide-like substances) as a function of MW. With a single injection (2 mL) and without sample pre-concentration, informative data for drinking water plant design and operation can be obtained. Those methods have been effectively applied to characterize feed waters and NF membrane foulants.; The extent of membrane fouling is dependent on water quality, membrane properties, and operational conditions. The feed waters from Oise River contained high calcium concentrations and high alkalinities. Inorganic salt precipitation (scaling) was indicated by FTIR, X-ray diffraction, X-ray fluorescence and SEM. Due to the decrease in solubility of CaCO_3(s) and CaSO _4(s) at high temperature, homogeneous crystallization occurred that led to less flux decline. At low temperature, in spite of increased solubility, heterogeneous crystallization with NOM adsorption was observed. (Abstract shortened by UMI.)...