Fouling of Reverse Osmosis Membrane with Effluent Organic Matter: Componential Role of Hydrophobicity

Organic matter dissolved in tertiary effluents (effluentorganicmatter, EfOM) is the predominant organic membrane foulant in tertiarywastewater reverse osmosis (RO) desalination, ultimately causing biofouling.The interrelated effects of EfOM fractions of different hydrophobicityand polarity on membrane performance were studied by (i) examiningeach fraction's overall effect on membrane permeability; (ii)analyzing the intrinsic hydraulic resistance induced by each fraction;(iii) studying their adsorption on the active layer of an RO membraneusing a quartz crystal microbalance with dissipation monitoring (QCM-D);(iv) assessing their "dry" molecular mass when adsorbedon polyamide using localized surface plasmon resonance (LSPR) sensing;(v) analyzing their hydrodynamic radii by dynamic light scattering(DLS); and (vi) characterization using excitation-emissionmatrix (EEM) analysis and parallel-factor (PARAFAC) modeling. Hydrophobicand transphilic neutral fractions (containing & SIM;12.5% totalorganic carbon) have the greatest effect on membrane flux reductionand the highest hydraulic resistance and adhere most strongly to polyamidesurfaces, resulting in the highest adsorbed "dry" mass.Therefore, in terms of their effect on RO permeate flux reduction,these fractions are the most detrimental in the EfOM mix. EEM analysisand associated PARAFAC modeling indicate that the main componentscausing this effect are mixtures of protein-like compounds, togetherwith humic-like substances. Novel LSPR-based analysis elucidated therole of the fractions most detrimental to membrane permeability throughmeasurement of dry mass surface concentration on a polyamide mimeticsensor. This study provides valuable insights into the roles of differentEfOM fractions in RO membrane fouling and enhances our understandingof fouling during tertiary wastewater desalination. The fundamental approach of this studyfor reducing RO membranefouling can improve the desalination process' energy and maintenancecosts as well as its carbon footprint.