Effects of Transmembrane Hydraulic Pressure on Performance of Forward Osmosis Membranes

Abstract

Forward osmosis (FO) is an emerging membrane separation process that continues to be tested and implemented in various industrial water and wastewater treatment applications. The growing interests in the technology have prompted laboratories and manufacturers to adopt standard testing methods to ensure accurate comparison of membrane performance under laboratory-controlled conditions; however, standardized methods might not capture specific operating conditions unique to industrial applications. Experiments with cellulose triacetate (CTA) and polyamide thin-film composite (TFC) FO membranes demonstrated that hydraulic transmembrane pressure (TMP), common in industrial operation of FO membrane elements, could affect membrane performance. Experiments were conducted with three FO membranes and with increasing TMP up to a maximum of 50 psi (3.45 bar). The feed solution was a mixture of salts and the draw solution was either a NaCl solution or concentrated seawater at similar osmotic pressure. Results revealed that TMP minimally affected water flux, reverse salt flux (RSF), and solute rejection of the CTA membrane. However, water flux through TFC membranes might slightly increase with increasing TMP, and RSF substantially declines with increasing TMP. It was observed that rejection of feed constituents was influenced by TMP and RSF.

Synthesis and characterization of novel high-performance thin film nanocomposite (TFN) FO membranes with nanofibrous substrate reinforced by functionalized carbon nanotubes

“…The smaller S values of the f-CNT filled substrates are favorable in reducing the ICP in the FO process. The S values of the f-CNT reinforced nanofibrous substrates are comparable with that of the most up-to date TFC FO membrane (~690 μm) from Hydration Technology Innovations (HTI, Albany) and TFC FO membrane (~365 μm) from Oasys (Boston) [9].…”

“…In an ODMP, including forward osmosis (FO) and pressure retarded osmosis (PRO), an osmotic pressure difference drives water flow through a semi-permeable membrane from a dilute feed water (FW) to a concentrated draw solution (DS) [1,2]. Besides the reduced energy input, other advantages of ODMP such as low fouling tendency and high cleaning efficiency make the ODMP attractive for a wide range of applications [3][4][5][6][7][8][9][10].…”

“…Early studies were limited to the commercial cellulose triacetate (CTA) FO membranes [13]. The recently emerged commercial and lab-made thin film composite (TFC) FO membranes consisting of a substrate synthesized via phase inversion and a polyamide rejection layer have demonstrated relatively higher water flux and better solute rejection [9,[14][15][16]. Nevertheless, their FO performance is still significantly limited by the severe ICP in the support layer, arising from the lack of pore connectivity (high tortuosity) [17].…”

Microalgae (Scenedesmus obliquus) dewatering using forward osmosis membrane: Influence of draw solution chemistry

“…The FO filtrations were considered complete when the concentration factor reached 4 (750 mL of permeate was extracted from the original algal suspension), which took 4.5-6.5 h depending on membrane type, orientation and draw solution composition. To minimize the impact of draw solution dilution on FO performance, draw solution concentration was monitored by conductivity measurement and maintained constant by dosing from a concentrated stock solution [27]. To quantify the permeate flux loss caused by algae fouling, baseline experiments were also conducted under identical conditions to the corresponding algae FO experiments, except no algae biomass was added into the feed solution.…”

System scale analytical modeling of forward and assisted forward osmosis mass exchangers with a case study on fertigation

“…To date, AFO performance has been evaluated by studying the impact of hydraulic pressure on FO membrane properties, which showed a significant increase in water flux while yielding lower reverse solute diffusion than predicted by the solution diffusion model [14]. The effects of hydraulic pressure, membrane properties, and orientation on AFO performance have also been investigated experimentally [12,15,16]. …”