NOVELTY - A membrane bioreactor comprising a membrane module cooperating with a porous pre-filtering component to define a compartment for receiving pretreated wastewater, and a turbulent flow-forming unit associated with the compartment for generating turbulent flow in the compartment, is new.    USE - The apparatus is used for treating wastewater.    ADVANTAGE - Strong turbulent flow is generated in the third compartment by virtue of the turbulent flow-forming unit. It acts on the outer porous membrane to minimize fouling of the membrane module. Therefore, the cleaning frequency of the membrane module is decreased and the operational life of the membrane module is prolonged. In addition, the wastewater turbulent flow formed in the compartment also acts on the porous pre-filtering component to avoid fouling of the porous pre-filtering component. Therefore, the cleaning frequency of the porous pre-filtering component is also decreased, and the operational life of the porous pre-filtering component is prolonged. Furthermore, the porous pre-filtering component is made from inexpensive materials. It can be replaced periodically.    DETAILED DESCRIPTION - A membrane bioreactor comprises a tank (10) adapted to receive wastewater; a porous pre-filtering component (20) mounted in the tank for conducting a primary filtration of the wastewater; a membrane module (30) mounted in the tank and disposed downstream of the porous pre-filtering component for conducting a secondary filtration of the wastewater pretreated by the porous pre-filtering component, wherein the membrane module cooperates with the porous pre-filtering component to define a compartment (113) for receiving the wastewater pretreated by the porous pre-filtering component; and a turbulent flow-forming unit (40) associated with the compartment for generating turbulent flow in the compartment.    DESCRIPTION OF DRAWING(S) - The figure shows a view of a membrane bioreactor.    Tank (10)    Inner space (11)    Bottom wall (12)    Porous pre-filtering component (20)    Pores (21, 33)    Membrane module (30)    Outer porous membrane (31)    Inner supporting mesh (32)    Outlet (34, 122)    Turbulent flow-forming unit (40)    Baffles (42)    Bottom hole (43)    Compartments (111-113)    Inlet (121)