A membrane filter (1, 36, 71, 83, 92, 101) for filtering a liquid (28, 37) to be filtered, comprising a. at least one membrane carrier (4, 41, 77, 96, 121), on which membranes are fastened, by means of which a liquid permeate (29, 44) can be filtered out of the liquid, wherein said membrane carrier features a permeate collection chamber (25, 47, 80, 90, 97, 124), to which the membranes are openly connected on the permeate side, as well as a permeate outlet (14, 48, 81) for discharging the permeate (29, 44) from the permeate collection chamber (25, 47, 80, 90, 97, 124), b. a gas distribution system (18, 62, 126, 133, 141, 147), which is arranged underneath the at least one membrane carrier (4, 41, 77, 96, 121) and comprises at least one trough (19, 63, 107, 113, 127, 134, 142, 148) that is open toward the bottom and closed on top, wherein said trough features a wall (20, 64, 109, 119, 129, 135, 143) with vertical slots (21, 65, 110, 115, 130, 136, 144), which are open toward the bottom, in order to distribute a gas (26, 38) into the liquid, and c. at least one gas inlet (13, 46, 108, 146, 149) into the gas distribution system (18, 62, 126, 133, 141, 147), characterized in that d. the at least one trough (19, 63, 107, 113, 127, 134, 142, 148) respectively features an inner edge (112, 117, 132, 140, 145) between adjacent slots (21, 65, 110, 115, 130, 136, 144) in at least a vertical section extending orthogonal to the wall (20, 64, 109, 119, 129, 135, 143), wherein said inner edge includes at any point an angle of less than 60° with the horizontal line at least in the region of a lower half (23, 69) of the slots (21, 65, 110, 115, 130, 136, 144). a. at least one membrane carrier (4, 41, 77, 96, 121), on which membranes are fastened, by means of which a liquid permeate (29, 44) can be filtered out of the liquid, wherein said membrane carrier features a permeate collection chamber (25, 47, 80, 90, 97, 124), to which the membranes are openly connected on the permeate side, as well as a permeate outlet (14, 48, 81) for discharging the permeate (29, 44) from the permeate collection chamber (25, 47, 80, 90, 97, 124), b. a gas distribution system (18, 62, 126, 133, 141, 147), which is arranged underneath the at least one membrane carrier (4, 41, 77, 96, 121) and comprises at least one trough (19, 63, 107, 113, 127, 134, 142, 148) that is open toward the bottom and closed on top, wherein said trough features a wall (20, 64, 109, 119, 129, 135, 143) with vertical slots (21, 65, 110, 115, 130, 136, 144), which are open toward the bottom, in order to distribute a gas (26, 38) into the liquid, and c. at least one gas inlet (13, 46, 108, 146, 149) into the gas distribution system (18, 62, 126, 133, 141, 147), characterized in that d. the at least one trough (19, 63, 107, 113, 127, 134, 142, 148) respectively features an inner edge (112, 117, 132, 140, 145) between adjacent slots (21, 65, 110, 115, 130, 136, 144) in at least a vertical section extending orthogonal to the wall (20, 64, 109, 119, 129, 135, 143), wherein said inner edge includes at any point an angle of less than 60° with the horizontal line at least in the region of a lower half (23, 69) of the slots (21, 65, 110, 115, 130, 136, 144).