The Water Flux Dynamic in a Hybrid Forward Osmosis-Membrane Distillation for Produced Water Treatment

Abstract

Standalone membrane distillation (MD) and forward osmosis (FO) have been considered as promising technologies for produced water treatment. However, standalone MD is still vulnerable to membrane-wetting and scaling problems, while the standalone FO is energy-intensive, since it requires the recovery of the draw solution (DS). Thus, the idea of coupling FO and MD is proposed as a promising combination in which the MD facilitate DS recovery for FO—and FO acts as pretreatment to enhance fouling and wetting-resistance of the MD. This study was therefore conducted to investigate the effect of DS temperature on the dynamic of water flux of a hybrid FO–MD. First, the effect of the DS temperature on the standalone FO and MD was evaluated. Later, the flux dynamics of both units were evaluated when the FO and DS recovery (via MD) was run simultaneously. Results show that an increase in the temperature difference (from 20 to 60 °C) resulted in an increase of the FO and MD fluxes from 11.17 ± 3.85 to 30.17 ± 5.51 L m−2 h−1, and from 0.5 ± 0.75 to 16.08 L m−2 h−1, respectively. For the hybrid FO–MD, either MD or FO could act as the limiting process that dictates the equilibrium flux. Both the concentration and the temperature of DS affected the flux dynamic. When the FO flux was higher than MD flux, DS was diluted, and its temperature decreased; both then lowered the FO flux until reaching an equilibrium (equal FO and MD flux). When FO flux was lower than MD flux, the DS was concentrated which increased the FO flux until reaching the equilibrium. The overall results suggest the importance of temperature and concentration of solutes in the DS in affecting the water flux dynamic hybrid process.

Advances in forward osmosis (FO) technology for enhanced efficiency and output: A critical review

“…Whereas with AL-DS orientation, increasing the flow rate (from 1.2 L/min to 3.2 L/min) at the draw side alone enhances the water flux by 36% (Hawari et al, 2016). This enhancement may be due to the reduced external concentration polarization on the membrane surface (Mat Nawi et al, 2020). At the same time, with AL-DS orientation, increasing the flow rate at the feed side alone (from 1.2 L/min to 3.2 L/min) increases the flux by 38.5%.…”

Technical Feasibility of Extraction of Freshwater from Produced Water with Combined Forward Osmosis and Nanofiltration

“…Various methods are being employed or developed aimed at the treatment of PW [9,16]. Among those or in the framework of certain management schemes, membrane separation processes may provide scalability and a suitable separation performance [8,11,15,[17][18][19][20][21][22][23][24][25][26][27][28][29][30][31][32][33]. The complexity of the PW composition presents a challenging task in selecting suitable unit operations for its treatment.…”

“…Forward osmosis is an osmotically driven membrane technology that has been suggested as a valid tool for the treatment of PW under certain circumstances, especially combined with other treatment units [19,21,22,27,28,[38][39][40][41][42][43][44][45][46][47][48][49][50]. The driving force of the water transport in an FO process is owed to the inherent osmotic pressure difference across the membrane.…”

Incorporation of Hydrophobic Silica in a Polyvinylidene Fluoride Membrane: Membrane Development and Performance Modeling

“…Membrane distillation (MD) is an emerging technology which utilizes low-quality heat sources [1][2][3] besides its flexibility for integration with other separation process, such as forward osmosis [4], crystallization [5], and reverse osmosis [6]. Despite these advantages, MD suffers from pore wetting and water condensation.…”