TECHNOLOGY FOCUS - INSTRUMENTATION AND TESTING - Preferred Components: The forward osmosis water treatment device further comprises a means for producing treated water from a remainder of the osmosis draw solution from which the draw solute has been separated by the recovery system, where the treated water includes water that has passed through the separation membrane by osmotic pressure from the feed solution to the osmosis draw solution.    TECHNOLOGY FOCUS - POLYMERS - Preferred Components: The polymer has a degree of substitution (DS) of: 0.5-2.5 per anhydrous glucose unit (with respect to R1-R6 being alkyl, cycloalkyl, heterocycloalkyl, aryl, heteroaryl, alkylaryl or arylalkyl); and 0.5-2.5 (preferably 0.8-2) per anhydrous glucose unit (with respect to -COR7). The skin layer has a higher density than the porous layer. The porous layer has a finger-like porous structure. The finger-like porous structure includes finger-like pores having a longest diameter of 10-50 mu m, an average of the longest diameter of the finger-like pores of 20-40 mu m, and a distance between adjacent finger-like pores of 1-20 mu m. The support layer has a porosity of 50-95%, and as defined by equation-1 of the specification. The polymer matrix layer is formed on one surface or both surfaces of the support layer. The polymer matrix layer: contacts the skin layer of the support layer; and includes a material comprising polyamide, crosslinked polyamide, polyamide-hydrazide, poly(amide-imide), polyimide, poly(allylamine)hydrochloride/poly(sodium styrene sulfonate), polybenzimidazole, and/or sulfonated poly(arylene ether sulfone), or a composite of an inorganic material and one of polyamide, crosslinked polyamide, polyamide-hydrazide, poly(amide-imide), polyimide, poly(allylamine)hydrochloride/poly(sodium styrene sulfonate), polybenzimidazole, and/or sulfonated poly(arylene ether sulfone). The separation membrane has a structure factor of 10-1500 defined by the equation-2 of the specification. The polymer solution comprises the polymer (a1) at a concentration of 9-15 wt.%. EXAMPLE - Hydroxypropyl methyl cellulose (70 g), acetic acid anhydride (1120 g) and pyridine (350 g) were introduced in a reactor (3 l) equipped with an agitator, and then the reaction mixture was agitated at 200 rpm and reacted at 90 degrees C for 3 hours to prepare acetylated cellulose ether. The acetylated cellulose ether (9 wt.%) and lithium chloride (4 wt.%) as a pore forming agent were mixed with dimethyl acetamide to prepare a polymer solution. The polymer solution was casted on a polyester nonwoven fabric to a thickness of 150 mu m. The casted substrate was immersed in a coagulation bath of deionized water at 25 degrees C. Deionized water was dripped to the formed membrane to clean remaining solvent. Then, the formed support layer was immersed in 1,3-phenylenediamine (2 wt.%) aqueous solution for 120 seconds, and excessive solution was removed from the membrane surface. The support layer in which 1,3-phenylenediamine was impregnated was immersed in 1,3,5-benzenetricarbonyl trichloride (0.1 wt.%) solution in Isopar-C (RTM: Isoparaffinic hydrocarbon solvent) for 60 seconds. During this process, a dense polymer layer of an ultra-thin polyamide layer was provided as a second layer thus providing a composite membrane. Then the composite membrane was washed with sodium carbonate (0.2 wt.%) aqueous solution and deionized water, to provide the separation membrane.