NOVELTY - The reactor comprises a wastewater feed line (18), inflow cyclones (4), in which the wastewater (13) is tangentially introducible, in a lower area of the reactor, a biomass sump in the lower area of the reactor, an intermediate separator (7), which is arranged above the cyclone and flows into a riser (9), a gas collecting chamber arranged in a head region of the reactor, from which biogas is removable over a connection line, an outlet system by which the treated water is conductible from the reactor, arranged in an upper area of the reactor, and a laminator.    USE - Reactor for the anaerobic treatment of wastewater through anaerobic biological conversion of organic matters and/or impurities by granulated and/or flaked biomass fixed on fluidizable carrier materials, where the organic compounds of the wastewater are decomposed to carbon dioxide, water and biogas such as methane in the reactor.    ADVANTAGE - The reactor can be easily manufactured with high reliability, is space-saving, and ensures continuous and efficient anaerobic treatment of the wastewater without requiring additional external pumping capacity.    DETAILED DESCRIPTION - The reactor comprises a wastewater feed line (18), inflow cyclones (4), in which the wastewater (13) is tangentially introducible, in a lower area of the reactor, a biomass sump in the lower area of the reactor, an intermediate separator (7), which is arranged above the cyclone and flows into a riser (9), a gas collecting chamber arranged in a head region of the reactor, from which biogas is removable over a connection line, an outlet system by which the treated water is conductible from the reactor, arranged in an upper area of the reactor, a laminator arranged in the upper area of the reactor for the rectification and/or pacification of the current, and a return funnel arranged in the upper area of the reactor. The inflow cyclone is vertically arranged in a reactor chamber (3), so that an upwardly directed turbulence flow forms within the cyclone. The outlet height of the riser is variable in the head region of the reactor and is adjustable by a height-adjustable outlet sleeve. The cyclone and the riser are connected with one another. The riser has a downwardly opened inlet funnel. The diameter of the inlet funnel is larger than the diameter of the cyclone. The laminator is formed by coaxially arranged tubular sections. The return funnel downwardly flows into the gas collecting chamber and upwardly flows into a downpipe, which is arranged from the head region of the reactor up to a center or lower area of the reactor in a running manner and coaxially surrounds the riser for recirculating liquid-solid mixture from the head region of the reactor up to lower area of the reactor. The downpipe and the riser are arranged in the head region of the reactor for conducting a three-phase mixture. The free flow cross-section of the downpipe corresponds to the free flow cross-section of the riser. The outer diameter of the inflow cyclone is smaller than the inner diameter of the reactor chamber, so that a circulatory flow forms around the cyclone. The inflow cyclone is arranged in a distance from a reactor base, where the distance is larger than the diameter of the inflow cyclone. The cyclone has a downwardly extending funnel-shaped inlet area, which extends up to an enlarged diameter around the factor of 1.6 compared to the diameter of the cyclone. The cyclone has a mixing zone above the inlet area. The inflow cyclones are parallely arranged. The cross-section area of the cyclone corresponds to 40% of the cross-section area of the reactor. The reactor, the cyclone, the laminator, an outgassing device, the riser, the downpipe and/or the inlet funnel have a rotational symmetric structure. The laminator, the riser, the downpipe and the inlet funnel are coaxially arranged within the reactor. An INDEPENDENT CLAIM is included for a method for the anaerobic treatment of wastewater through anaerobic biological conversion of organic matters and/or impurities by granulated and/or flaked biomass fixed on fluidizable carrier materials in a reactor.    DESCRIPTION OF DRAWING(S) - The diagram shows a cross-sectional view of a reactor for anaerobic treatment of wastewater.    Reactor chamber (3)    Inflow cyclones (4)    Intermediate separator (7)    Riser (9)    Wastewater (13)    Feed line. (18)