AWWA WQTC62468

AWWA WQTC62468 Identification of Organic Foulants of Low and High Pressure Membranes
Conference Proceeding by American Water Works Association, 11/01/2005

Habarou, H.; Heim, V.; Croue, J.P.

More info

Full Description

The objective of this study was to characterize and identify the nature of the organic foulants responsible forflux declines of low and high pressure membranes.Experiments with lab-scale or pilot scale units were conducted on both clarified surface waters duringperiods of more intense microbial activity and on solutions of natural organic matter (NOM) (especially cell wall residues andalso humic-like substances). HPSEC and Pyrolysis GC/MS analyses were the two major analytical toolsused in this study. Several TOF SIMS and amino acids and aminosugars analyses were also performed.This work confirmed that during intense microbial activity in the source water (spring, summer time),conventionally treated water exert stronger membrane fouling. This study showed that the organicfoulant that remains after backwash and chemical cleaning was a mixture of several biopolymers(proteins, polysaccharides, aminosugars and polyhydroxyaromatics). Aminosugars and polysaccharideswhich originate from microbial activity (microbial cell wall residues and/or exopolymers from DOMconstituents and/or biofilm) appeared to be the major constituents of the fouling material. However,results from experiments with NOM fractions have shown that aromaticity appears to be a secondaryparameter which influences PES membrane fouling.The second part of this article is focused on the membrane foulant autopsy conducted on nanofiltrationmembranes isolated before and after cleaning from the M¿¿ry sur Oise filtration train. Elementalanalysis, Pyrolysis GC/MS, FT-IR, 13C- NMR analyses were performed on both insoluble and solublephases of the deposit extracted from nanofiltration (NF) modules. Again, results confirmed the microbial origin of thefouling material. Polysaccharides and aminosugars were found to be the major organic constituents ofthe fouling material. In addition, the inorganic content (calcium, phosphorous and aluminum as majorconstituents) was found to increase significantly from stage 1 to stage 3 of the filtration train. Afterchemical cleaning a significant reduction of the inorganic content was noticed, however the organiccomposition of the foulant remained unchanged. Includes 8 references, table, figures.