The effects of gas distributor on hydrodynamics in an air-water shallow bubble column reactor are investigated. Three types of distributors, namely, single nozzle, perforated plate and porous plate are being studied. The overall gas holdup, bubble size distributions and bubble rise velocity distributions are studied over a range of superficial gas velocities. The results show that single nozzle is not suitable for shallow bed operation. While perforated plate and porous plate distributors have comparable behaviour in the absence of solids, the addition of solids particles causes the two distributors to behaviour differently. The presence of solids promotes bubble coalescence for perforated plate distributor while the same inhibits bubble coalescence for porous plate distributor.