A rotor (100) of a gas dispersion arrangement, comprising a cover disc (1), air slots (2) arranged to protrude away from the cover disc (1), the air slots (2) defining an interior space (3) in the interior of the rotor, an air channel (4) connected to the air slot (2) for supplying air to be dispensed in slurry, and slurry slots (5) arranged between and an alternating way with the air slots (2) around the interior space (3). The slurry slots (5) are in fluid communication with the interior space (3), and radially extending blades (6) arranged for separating the air slot (2) from adjacent slurry slots (5). The cover disc (1) comprises at least one through-hole (7) extending from an upper surface (8) of the cover disc to at least one of the slurry slots (5).