Diminished swelling of cross-linked aromatic oligoamide surfaces revealing a new fouling mechanism of reverse-osmosis membranes.
Swelling of the active layer of reverse osmosis (RO) membranes has an important effect on permeate water flux. The effects of organic- and biofouling on the swelling of the RO membrane active layer and the consequent changes of permeate flux are examined here. A cross-linked aromatic oligoamide film that mimics the surface chemistry of an RO polyamide membrane was synthesized stepwise on gold-coated surfaces. Foulant adsorption to the oligoamide film and its swelling were measured with a quartz crystal microbalance, and the effects of fouling on the membrane's performance were evaluated. The foulants were extracellular polymeric substances (EPS) extracted from fouled RO membranes and organic compounds of ultrafiltration permeate (UFP) from a membrane bioreactor used to treat municipal wastewater. The adsorbed foulants affected the swelling of the cross-linked oligoamide film differently. EPS had little effect on the swelling of the oligoamide film, whereas UFP significantly impaired swelling. Permeate flux declined more rapidly under UFP fouling than it did under EPS. Foulant adsorption was shown to diminish swelling of the aromatic oligoamide surfaces. Among the already known RO membrane fouling mechanisms, a novel RO fouling mechanism is proposed, in which foulant-membrane interactions hinder membrane swelling and thus increase hydraulic resistance.
Department of Desalination and Water Treatment, Zuckerberg Institute for Water Research, Jacob Blaustein Institutes for Desert Research, Ben-Gurion University of the Negev, Sede Boqer Campus, Midreshet Ben-Gurion 84990, Israel.
Wang
W
Ying
Department of Desalination and Water Treatment, Zuckerberg Institute for Water Research, Jacob Blaustein Institutes for Desert Research, Ben-Gurion University of the Negev, Sede Boqer Campus, Midreshet Ben-Gurion 84990, Israel.
Rajender
R
Kumar
Department of Desalination and Water Treatment, Zuckerberg Institute for Water Research, Jacob Blaustein Institutes for Desert Research, Ben-Gurion University of the Negev, Sede Boqer Campus, Midreshet Ben-Gurion 84990, Israel.
Moshe
M
Herzberg
Department of Desalination and Water Treatment, Zuckerberg Institute for Water Research, Jacob Blaustein Institutes for Desert Research, Ben-Gurion University of the Negev, Sede Boqer Campus, Midreshet Ben-Gurion 84990, Israel.
Roni
R
Kasher
D000327:Adsorption; D057219:Biofouling; D003432:Cross-Linking Reagents / Q000737:chemistry*; D006841:Hydrocarbons, Aromatic / Q000737:chemistry*; D008567:Membranes, Artificial; D009757:Nylons / Q000737:chemistry*; D009995:Osmosis; D011134:Polysaccharides / Q000737:chemistry; D058525:Quartz Crystal Microbalance Techniques; D013499:Surface Properties; D014462:Ultrafiltration; D062065:Wastewater / Q000737:chemistry; D018508:Water Purification
D003432:Cross-Linking Reagents; D006841:Hydrocarbons, Aromatic; D008567:Membranes, Artificial; D009757:Nylons; D011134:Polysaccharides; D062065:Wastewater