A membrane module is used for the water treatment that performs solid-liquid separation. As the membrane module, for example, there is known a hollow fiber membrane module having a hollow fiber membrane bundle in which a plurality of hollow fiber membranes is drawn and aligned in one direction, and holding members that hold the hollow fiber membrane bundle at both ends of the hollow fiber membrane in the length direction thereof. In recent years, making a plurality of membrane modules into a unit is performed due to an increase in the amount of raw water to be treated.
As a membrane module unit in which a plurality of membrane modules is made into a unit, for example, the following membrane module unit is known.
(1) A membrane module unit in which both ends of a plurality of hollow fiber membrane modules are connected to water collection headers fixed to a substantially rectangular parallelepiped frame (Patent Documents 1 and 2).
(2) A membrane module unit that is made into a unit by housing a plurality of hollow fiber membrane modules within a substantially rectangular parallelepiped frame, and holding both ends of the modules by the frame (Patent Document 3).
However, there are the following problems in the units (1) and (2).
(i) First, it is necessary to assemble the frame.
(ii) Since a plurality of the hollow fiber membrane modules should be attached to the frame one by one, the assembly of the units is complicated, and since a plurality of the hollow fiber membrane modules is removed one by one from the units, disassembly and maintenance (washing, checking, or the like) are complicated.
(iii) The structure of the units becomes complicated, in order to enhance sealing performance or durability against vibration, stress or the like at a connection between the collection water header or the frame and the hollow fiber membrane modules, or to suppress vibration of the hollow fiber membrane modules themselves.
Particularly, in recent years, since the membrane modules and the unit thereof are enlarged due to a further increase in the amount of raw water to be treated, it becomes difficult to easily handle the membrane modules and the unit. Additionally, with the enlargement, in the frame or the membrane modules, dimensional errors are likely to be caused, or distortion is likely to occur. Therefore, it becomes difficult to reliably couple and fix a plurality of the membrane modules.