Characteristics and fouling behaviors of Dissolved Organic Matter fractions in a full-scale submerged membrane bioreactor for municipal wastewater treatment
Résumé
Dissolved Organic Matter (DOM) taken in a full-scale membrane bioreactor (MBR) was fractionated in terms of size and hydrophobicity using dialysis bags and XAD resins. Colloids, hydrophobic (HPO) and transphilic (TPI) fractions were isolated and characterized using fluorescence spectroscopy, size exclusion chromatography and thermo-chemolysis. Results revealed a high proportion of protein materials in the Colloids fraction, while HPO and TPI fractions were mostly constituted of humic-like materials. Then, fouling propensities and reversibility of single and mixed fractions were evaluated throughout filtration tests. Results emphasized the major role of Colloids in a reversible bio-cake formation, with a flux reduction of 67% and a flux recovery after cleanings of 35%. HPO and TPI fractions led to less fouling (flux reduction of 51% and 38%, respectively), but stronger adsorption, resulting in higher irreversible fouling (flux recovery after cleanings of 20% and 9%, respectively). Filtrations of mixed fractions confirmed that physicochemical interactions between DOM fractions influence membrane fouling. When Colloids were mixed with HPO, TPI, or HPO + TPI, fouling effect was respectively 13%, 27% and 35% higher than expected. However, higher efficiencies of cleaning procedures were observed on mixed foulant deposition, especially for relaxation step (up to 25%). (C) 2018 Elsevier B.V. All rights reserved.