Understanding fouling behaviour of ultrafiltration membrane processes and natural water using principal component analysis of fluorescence excitation-emission matrices

Fouling is a major obstacle for maintaining efficient membrane-based drinking water treatment processes. Natural organic matter (NOM) components such as humic substances (HS)- and protein-like matter as well as colloidal/particulate matter are known to be the major membrane foulants in ultrafiltration-based drinking water processes. In this study, a fluorescence excitation-emission matrix (EEM) approach was used for characterization of these major membrane foulants. Unlike most NOM and colloidal/particulate matter characterization techniques, this method can provide fast and consistent analyses with high instrumental sensitivity. Principal component analysis (PCA) of fluorescence EEM measurements collected during cross-flow ultrafiltration of river water was used to extract principal components (PCs) that contained information relevant to membrane fouling. These PCs were related to the major membrane foulants, HS, protein-like and colloidal/particulate matter present in natural water. PC score analysis revealed that colloidal/particulate matter mostly contributed to reversible fouling. HS- and protein-like matter were largely responsible for irreversible fouling behaviour. Fluorescence EEMs of the foulants extracted from the membranes also revealed different rejection characteristics for two different membranes, 60 kDa and 20 kDa. The proposed method proved suitable for identifying the major foulant components and their contribution to reversible and irreversible membrane fouling, illustrating its potential for monitoring and controlling membrane fouling in drinking water treatment applications.