Pilot-scale evaluation of forward osmosis membranes for volume reduction of industrial wastewater

Abstract

Water treatment is a key aspect for the sustainable management of oil & gas operations. Osmotic concentration (OC) is an advanced water treatment process, adapted from forward osmosis (FO), that does not require water recovery from the draw solution. In this study, two commercial hollow fiber FO membranes [Module 1, cellulose triacetate (CTA) and Module 2, thin film composite (TFC)] were evaluated at pilot scale using actual process water obtained from a gas production facility. The evaluation focused on assessing the membrane productivity, fouling potential and chemical cleaning efficiency while normalizing the performance using a theoretical model that account for the variability of the operating conditions. Performance tests showed that Module 2 has a higher flux compared to Module 1, 9.9 L/m2·h vs 1.7 L/m2·h; and lower specific reverse solute flux (RSF) for most of the ions. Additionally, Module 1 benchmark experiment showed a 13% flux loss attributed to inorganic fouling (calcium phosphate precipitation) while the flux loss in Module 2 was <5% possibly due to enhanced module hydrodynamics and variation in membrane chemistry. Chemical cleaning (citric acid) proved to be successful in restoring the flux for Module 1. From the 8.1 mg/L organic carbon present in the feed, advanced organic characterization revealed that certain group of hydrophilic organics are able to pass through Module 1, but not Module 2, translating to a specific forward organic solute flux of 0.9 mg/L and 0.1 mg/L for Module 1 and 2, respectively. Finally, key sustainable and environmental considerations were presented in support of further development of process implementation. The OC process has strong potential for full-scale installation; however, demonstrating its performance in the field would be the next step necessary for successful implementation of the technology.