Evaluation of the transport parameters and physiochemical properties of forward osmosis membranes after treatment of produced water

• The effect of exposing FO membranes to oil and gas wastewater was investigated.
• Transport and structural parameters were modeled for three commercial FO membranes.
• Minor changes to CTA and traditional TFC FO membranes were observed.
• 50% reduction in reverse salt flux of a surface-modified TFC membrane was recorded.
• Surface-modified TFC crosslinking density decreases after exposure to feed water.

The application of semipermeable membranes for dewatering of complex oil and gas wastewaters continues to be a topic of increasing interest. Several studies have explored the fouling propensity and contaminant rejection of osmotically driven membranes during forward osmosis (FO) treatment of produced waters; however, none have investigated changes in membrane transport and physiochemical properties after exposure to these feed streams. In this study we discuss the impacts of produced water exposure on the transport and active layer surface properties of cellulose triacetate (CTA) and polyamide thin-film composite (TFC) FO membranes. While produced water exposure yields some, albeit minor changes to the membrane performance and surface characteristics of the CTA and the traditional TFC membranes, close to 50% reduction in reverse salt flux and contaminant transport was observed for a surface-modified TFC FO membrane; only minimal changes in water permeability were recorded. Results of this study demonstrate the chemical and physical robustness of FO membranes for treatment of oil and gas wastewaters, and they highlight a knowledge gap that exists in membrane polymer selection and contaminant interactions with the membrane polymer matrix that should be further addressed in future membrane fouling studies.

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