**2. Principle of forward osmosis**

Forward osmosis is an emerging technology using a semipermeable ultrathin membrane to treat water or wastewater, and the membrane is typically thinner than RO membranes. Similar to the structure of thin film RO membranes, an FO membrane typically consists of an active layer and a support layer. In a commercially available thin film composite (TFC) FO membrane, the active layer is polyamide (PA), and the support layer is mainly made of polysulfone (PSf) or polyethersulfone (PES). An FO system generally consists of an FO module/cell for holding FO membranes, a draw solute recovery unit and pumps for circulating feed and draw solution (**Figure 2**). The FO module/cell is classified into flat sheet, hollow fiber, and spiral wound configurations, mainly depending on the operating scale. Although FO takes some advantages of an osmotically driven process, such as less membrane fouling, low energy requirement and operating cost, over

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**Figure 3.**

*Association of Polyethylene Glycol Solubility with Emerging Membrane Technologies, Wastewater…*

pressure-driven processes of nanofiltration (NF), and reverse osmosis (RO) in a similar membrane separation range, it still encounters some challenges in a wide range of practical applications for wastewater treatment and desalination. Jampani and Raghavarao purified and concentrated red cabbage (*Brassica oleracea* L.) anthocyanins by integrating osmotic membrane distillation and FO processes with a PEG-4000 and MgSO4 (14.8/10.3%, w/w) extraction system [11]. Later, they used similar technologies to separate and concentrate Jamun anthocyanins by using PEG 6000 in the extraction system [12]. To test the performance of FO membranes, a series of PEG (10 and 20 kDa) and PEO (100, 600 and 1000 kDa) were used to determine molecular weight cutoff (MWCO), pore size, and distribution of a hydrophilic support layer during the fabrication of a TFC FO

Membrane distillation (MD) is another emerging technology in membrane separation, which uses a hydrophobic, microporous membrane to treat water or wastewater through a thermally driven separation process. In an MD process, the

*Configurations of membrane distillation. (a) DCMD. (b) AGMD. (c) SGMD. (d) VMD.*

*DOI: http://dx.doi.org/10.5772/intechopen.89060*

**3. Principle of membrane distillation**

membrane [13].

**Figure 2.** *Schematic of a forward osmosis system with draw solute recovery.*

*Association of Polyethylene Glycol Solubility with Emerging Membrane Technologies, Wastewater… DOI: http://dx.doi.org/10.5772/intechopen.89060*

pressure-driven processes of nanofiltration (NF), and reverse osmosis (RO) in a similar membrane separation range, it still encounters some challenges in a wide range of practical applications for wastewater treatment and desalination. Jampani and Raghavarao purified and concentrated red cabbage (*Brassica oleracea* L.) anthocyanins by integrating osmotic membrane distillation and FO processes with a PEG-4000 and MgSO4 (14.8/10.3%, w/w) extraction system [11]. Later, they used similar technologies to separate and concentrate Jamun anthocyanins by using PEG 6000 in the extraction system [12]. To test the performance of FO membranes, a series of PEG (10 and 20 kDa) and PEO (100, 600 and 1000 kDa) were used to determine molecular weight cutoff (MWCO), pore size, and distribution of a hydrophilic support layer during the fabrication of a TFC FO membrane [13].
