Membrane separation device
A membrane separation device includes a plurality of membrane elements each having a separation membrane arranged on front and back sides of a flat filter plate, wherein the membrane elements are oriented vertically and arranged in an array separated by a fixed distance such that the separation membranes are facing one another. A narrowing member is provided outside of the membrane element arranged at the outermost position along the arrangement direction, the narrowing member being disposed at least in a vicinity of a bonding portion of the filter plate and the separation membrane along the vertical direction thereof so as to be separated from the outermost membrane element by a predetermined distance smaller than the fixed distance T, thereby avoiding rupture of the separation membrane provided on outer side of the outermost membrane element even if aeration is continued in a state in which the filtering operation is stopped.
1. A membrane separation device comprising:
a plurality of membrane elements arranged in a standing position with a predetermined gap provided therebetween such that the plurality of membrane elements are separated from one another by a fixed distance so as to form an open flow passage, each of the plurality of membrane elements including:
a membrane support body in a form of a flat panel or sheet having a front surface and a rear surface; and
a separation membrane wrapped around the membrane support body so as to substantially cover the front surface and the rear surface by turning over at an upper side edge of the membrane support body, and expose at least one side end portion of the membrane support body, the separation membrane being attached to the membrane support body by a longitudinal bonding portion provided along the at least one side end portion;
a water collection case to which the plurality of membrane elements are connected by inserting thereto the at least one side end portion of each membrane support body, the water collection case having a water collection space therein into which treated water filtered by the plurality of membrane elements is collected;
a cover member provided adjacent to at least one outermost membrane element of the plurality of membrane elements; and
a narrowing member provided on the cover member so as to face the longitudinal bonding portion of the at least one outermost membrane element such that the narrowing member is separated from the at least one outermost membrane element by a predetermined distance smaller than the fixed distance, a remaining portion of the cover member without the narrowing member being separated from the at least one outermost membrane element by the fixed distance.
2. The membrane separation device according to claim 1 , wherein the narrowing member is provided at least near an upper portion of the longitudinal bonding portion.
3. The membrane separation device according to claim 1 , wherein the separation membrane is turned over at least at an upper side edge of the membrane support body so as to be disposed on both of the front and rear surfaces of the membrane support body.
4. The membrane separation device according to claim 1 , wherein the predetermined distance is set equal to or smaller than a half of the fixed distance.
5. The membrane separation device according to claim 2 , wherein the separation membrane is turned over at least at an upper side edge of the membrane support body so as to be disposed on both of front and rear sides of the membrane support body.
6. The membrane separation device according to claim 2 , wherein the predetermined distance is set equal to or smaller than a half of the fixed distance.
7. The membrane separation device according to claim 3 , wherein the predetermined distance is set equal to or smaller than a half of the fixed distance.
8. The membrane separation device according to claim 1 , wherein the narrowing member is configured to restrict bulging of the separation membrane from a surface of the membrane support body adjacent to the longitudinal bonding portion in the at least one outermost membrane element.
9. The membrane separation device according to claim 1 , wherein the membrane support body includes a plurality of flow passages provided therethrough, each of the plurality of flow passages extending in a horizontal direction and having an opening on both ends of the membrane support body.
10. The membrane separation device according to claim 9 , wherein the front and rear surfaces of the membrane support body have a plurality of minute holes in communication with the flow passages.
11. The membrane separation device according to claim 1 , wherein the longitudinal bonding portion is formed in a connecting portion of the membrane support body and the water collection case.
12. The membrane separation device according to claim 1 , wherein the longitudinal bonding portion is formed outside the water collection case.
13. The membrane separation device according to claim 1 , wherein the cover member is not provided with a separation membrane.