To improve the linear velocity of fluid flowing in membrane surfaces of reverse osmosis membrane elements to suppress concentration polarization and making a reverse osmosis membrane separation apparatus sufficiently exhib capability of the reverse osmosis membrane elements by installing a reverse osmosis membrane module in which a plurality of reverse osmosis membrane elements are connected in series and specifying the cross-section surface area of a raw water flow route of the reverse osmosis membrane elements.
The reverse osmosis membrane part is composed of a module 3 to which a plurality of reverse osmosis membrane elements are boaded. In this case, the reverse osmosis membrane element 1 in the upstream side is made to have a wider cross-section surface area of a raw water flow route than the reverse osmosis membrane element 12 in the downstream side. The raw water passed through a raw water intake route 4 and pressurized by a pressurizing pump 5 and led to the module 3. Consequently, the raw water is subjected to reverse osmosis membrane treatment by the reverse osmosis membrane element 1 and the passed water is taken out through a passed water discharge route 7. The concentrated water which is not passed through the reverse osmosis membrane element 1 is led to the reverse osmosis membrane element 2 and treated by the element 2 and the passed water is discharged through the passed water discharge route 7 and concentrated water is discharged through a concentrated water discharge route 6.
KIHARA MASAHIRO
TANIGUCHI MASAHIDE
