A hollow fiber membrane module, a hollow fiber membrane module unit using the hollow fiber membrane module, and a water treatment method using the module or the module unit enable the efficient contact of microorganisms on the surface of a membrane with a gas, the module and the unit having excellent durability. The unique design featuring a plurality of orifices in spherical surface minimizes splashing and stirring the water around the user. Furthermore, the harmonic suppression apparatus can provide a fixed or variable reactive power. First, voltage levels of first and second terminals of the transistors are equalized to a ground voltage in a pre-discharge period. In one example embodiment, the hinge mechanism comprises a groove in the base portion, a guiding feature on the moveable portion that engages the groove, and a link attached to both the base portion and the moveable portion of the electronic device, the link relating relates the motions of the two portions such that the electronic device opens as the guiding feature travels along the groove.