Abstract: According to the present invention, it is possible to obtain a separation membrane element which has an element configuration having high fresh water production performance and high removal performance, has an improved membrane surface linear velocity whereby fouling due to hardly-soluble salts (scales) or organic matters is less likely to occur on the membrane surface particularly in high recovery ratio operation, and is excellent in fresh water production performance and removal performance over a long period of time.

Abstract: The present invention pertains to a semipermeable composite membrane having a support film and a separation function layer, wherein, (A) in a semipermeable composite membrane equilibrated under specific conditions, the half value width H of an absorption peak between 3900 cm?1 and 2900 cm?1 in a difference spectrum Sd obtained by subtracting IR spectrum S2 from IR spectrum S1 is 355-373, and (B) in the IR spectrum S1, the value F obtained by dividing the area of the absorption intensity between 3900 cm?1 and 2900 cm?1 by the absorbance at the peak top between 1690 cm?1 and 1630 cm?1 is at least 850.

Abstract: According to the present invention, it is possible to obtain a separation membrane element which has an element configuration having high fresh water production performance and high removal performance, has an improved membrane surface linear velocity whereby fouling due to hardly-soluble salts (scales) or organic matters is less likely to occur on the membrane surface particularly in high recovery ratio operation, and is excellent in fresh water production performance and removal performance over a long period of time.