Pilot-scale investigation of drinking water ultrafiltration membrane fouling rates using advanced data analysis techniques.

A pilot-scale investigation of the performance of biofiltration as a pre-treatment to ultrafiltration for drinking water treatment was conducted between 2008 and 2010. The objective of this study was to further understand the fouling behaviour of ultrafiltration at pilot scale and assess the utility of different foulant monitoring tools. Various fractions of natural organic matter (NOM) and colloidal/particulate matter of raw water, biofilter effluents, and membrane permeate were characterized by employing two advanced NOM characterization techniques: liquid chromatography - organic carbon detection (LC-OCD) and fluorescence excitation-emission matrices (FEEM) combined with principal component analysis (PCA). A framework of fouling rate quantification and classification was also developed and utilized in this study. In cases such as the present one where raw water quality and therefore fouling potential vary substantially, such classification can be considered essential for proper data interpretation. The individual and combined contributions of various NOM fractions and colloidal/particulate matter to hydraulically reversible and irreversible fouling were investigated using various multivariate statistical analysis techniques. Protein-like substances and biopolymers were identified as major contributors to both reversible and irreversible fouling, whereas colloidal/particulate matter can alleviate the extent of irreversible fouling. Humic-like substances contributed little to either reversible or irreversible fouling at low level fouling rates. The complementary nature of FEEM-PCA and LC-OCD for assessing the fouling potential of complex water matrices was also illustrated by this pilot-scale study.

Occurrence, source, and fate of dissolved organic matter (DOM) in a pilot-scale membrane bioreactor.

In this study, the fate of carbohydrates, proteins, and humic substances in feedwater, sludge supernatant, and permeate of a pilot-scale membrane bioreactor (MBR) was investigated. Over 10 months, carbohydrates were observed to have a lower bioelimination degree (45%) and higher rejection degree (79%) than those of proteins (81% and 44%, respectively), which led to a high carbohydrate/protein ratio of dissolved organic matter (DOM) in sludge supernatant. The batch tests showed that DOM derived from feedwater and bound extracellular polymeric substances (EPS) was eliminated by activated sludge via biosorption and biodegradation. The proteins in bound EPS and feedwater were also found to have much higher biosorption potential (27% and 31%, respectively) than humic substances (11% and 17%, respectively) and carbohydrates (16% and 14%, respectively), indicating that proteins had a high affinity with sludge flocs. The results also showed that carbohydrates and humic substances in bound EPS were more difficult to be eliminated by activated sludge. In addition, the batch tests confirmed that feedwater was mainly composed of readily biodegradable matter, and bound EPS was mainly composed of slowly biodegradable matter. Size exclusion chromatography with continuous organic carbon and UV(254) detection (LC-OCD) showed that large-size substances (i.e., carbohydrates and macromolecular proteins) in sludge supernatant might originate from bound EPS, which can be rejected by membranes. The LC-OCD analysis, together with the results obtained from batch tests, suggested bound EPS might be the most important source of DOM in the sludge suspension.