Forward Osmosis as Concentration Process: Review of Opportunities and Challenges

Abstract

In the past few years, osmotic membrane systems, such as forward osmosis (FO), have gained popularity as “soft” concentration processes. FO has unique properties by combining high rejection rate and low fouling propensity and can be operated without significant pressure or temperature gradient, and therefore can be considered as a potential candidate for a broad range of concentration applications where current technologies still suffer from critical limitations. This review extensively compiles and critically assesses recent considerations of FO as a concentration process for applications, including food and beverages, organics value added compounds, water reuse and nutrients recovery, treatment of waste streams and brine management. Specific requirements for the concentration process regarding the evaluation of concentration factor, modules and design and process operation, draw selection and fouling aspects are also described. Encouraging potential is demonstrated to concentrate streams more than 20-fold with high rejection rate of most compounds and preservation of added value products. For applications dealing with highly concentrated or complex streams, FO still features lower propensity to fouling compared to other membranes technologies along with good versatility and robustness. However, further assessments on lab and pilot scales are expected to better define the achievable concentration factor, rejection and effective concentration of valuable compounds and to clearly demonstrate process limitations (such as fouling or clogging) when reaching high concentration rate. Another important consideration is the draw solution selection and its recovery that should be in line with application needs (i.e., food compatible draw for food and beverage applications, high osmotic pressure for brine management, etc.) and be economically competitive.

Insights into the Influence of Membrane Permeability and Structure on Osmotically-Driven Membrane Processes

“…OM applications can use different types of saline water, which may contain sparingly soluble ions and impurities with high concentrations. For example, in desalination-hybrid processes where seawater or seawater desalination brine is used, a great amount of scaling precursors like Ca 2+ , Mg 2+ , SO 4 2− , and CO 3 2− exist [54]. Sparingly soluble salts may precipitate and deposit on membrane during operation.…”

“…Niche applications using DSs without the need of regeneration (e.g., seawater [ 1 ], desalination brine [ 2 ], or fertilizer solutions [ 3 ]) are attractive due to the elimination of energy-intensive DS re-concentration step. OM and hybrid OM processes have been explored for diverse fields [ 4 ], such as wastewater reuse [ 5 , 6 , 7 ], desalination [ 8 , 9 , 10 , 11 ], osmotic membrane bioreactor [ 12 ], energy production [ 13 , 14 , 15 ], and food processing [ 16 , 17 ].…”

“…Niche applications using DSs without the need of regeneration (e.g., seawater [1], desalination brine [2], or fertilizer solutions [3]) are attractive due to the elimination of energy-intensive DS reconcentration step. OM and hybrid OM processes have been explored for diverse fields [4], High-performance membranes are crucial for OM technologies. Typical osmotic membranes consist of an active rejection layer and a porous support layer.…”

State-of-the-Art and Opportunities for Forward Osmosis in Sewage Concentration and Wastewater Treatment

“…Moreover, the performance of the FO system is associated with many factors, including FO membrane properties, areas of application, and operation conditions. Although there are a number of comprehensive reviews reported in recent years, they mainly focus on the fabrication and modification methods of FO membranes [ 30 ], the utilisation of FO membranes for desalination [ 31 ], and the concentration process [ 32 ]. In this work, we aim to provide a concise review of the latest development of applying FO technology for sewage concentration and wastewater treatment and focus on the interaction among membrane materials, feed solution properties, draw solution properties, and system operating conditions during the application.…”

Alleviation of Reverse Salt Leakage across Nanofiber Supported Thin-Film Composite Forward Osmosis Membrane via Heat-Curing in Hot Water

“…It emerges with its distinctive advantages of lower pollution tendency, higher resilience after cleaning and lower energy consumption than conventional pressure-driven membrane technologies. FO technology has shown intriguing potentials in various application fields, such as desalination, wastewater treatment, food and drug concentration, and power generation [ 3 , 4 , 5 , 6 ].…”