A hybrid dead-end/cross-flow forward osmosis system for evaluating osmotic flux performance at high recovery of produced water

Forward osmosis (FO) has recently been considered as a means of treating or concentrating produced water because of its low fouling propensity at high recoveries. However, while numerous studies have been published on produced water treatment with FO, many benchtop studies use “coupon” type membrane systems that can only operate at limited recovery because of large holdup volumes and small membrane areas. Newly available commercial elements could be used, but working with such dirty waters would be costly as elements would need regular replacement. In this work, we propose a new method for testing the efficacy of forward osmosis that enables high water recovery using coupon based testing systems. Our hybrid dead-end/cross-flow filtration cell operates in a dead-end mode on the feed side and a cross-flow mode on the draw side, maximizing the recovery of the feed while minimizing dilution of the draw. We demonstrate the value of this type of testing apparatus using an unprocessed produced water provided by Chevron Corporation. This water, which contains small quantities of oil and approximately 7500 ppm total dissolved solids (TDS), could be concentrated by up to 20 fold using this approach.