Monitoring UF membrane performance treating surface-groundwater blends: limitations of FEEM-PARAFAC on the assessment of the organic matter role

Abstract

The decrease of water quantity and quality in water scarcity areas is palliated by improving water treatments with membrane technologies. System performance and efficiency, and then cost, is mainly affected by membrane fouling, which is still not well understood and controlled appropriately. In this study, the influence of content and composition of dissolved organic matter (DOM) on a membrane ultrafiltration (UF) stage from a full-scale UF stage in a drinking water treatment plant (DWTP) fed with surface water, groundwater (or blends of them) was investigated. Excitation-emission matrix (EEM) fluorescence spectroscopy coupled with parallel factor analysis (PARAFAC) was used to characterize and assess DOM changes in water samples Water streams feeding the UF stage showed high variability in DOM content and composition. FEEM-PARAFAC analysis allowed the differentiation of seven different organic components. Additionally to the characterization and monitoring of DOM in the full-scale UF stage, a bench scale UF pilot was run to experimentally correlate the impact of water quality with membrane performance. The experiments included testing synthetic solutions of model foulants (synthetic humic acid and bovine serum albumin) and blends of complex waters. To quantify fouling, the total fouling index (TFI) and the hydraulically irreversible fouling index (HIFI) were calculated for each filtration run. According to the results obtained, the correlation plots between the PARAFAC components and the fouling indices pointed at microbial byproducts (C1) and humic-like components (C2, C4, C5) as the ones showing higher correlations.