Textile industry is being a very demanding consumer of high-quality water with highest wastewater discharge. Membrane bioreactor (MBR) was employed widely to treat dying effluents due to its distinct advantages over conventional techniques. This study investigated the potential of biological treatment employing a microbial community 'IHK22' under MBR laboratory-scale conditions to decolourize reconstituted textile wastewater in order to be reused. First, the bioreactor was conducted at a low biomass concentration of 4 g(MLVSS) . L-1. Decolourization performances were maintained at very high rates (91-100 %) for dye mass loading rates in the range of 1.25-2.5 mg g(MLVSS) d(-1). Then, the dye concentration was increased to 7.5 mg gmLvss-1 d-1, the decolourization performances of the MBR have been affected (80-87 %). When the biomass concentration has been increased to 8 g(MLVSS) . L-1, thus, a total MBR decolourization was then observed (100 %). Under 320 mg g(MLVSS) d(-1) and regardless of the operating period of the MBR, all the microorganisms and microfiltration membrane allow the elimination of most soluble organic matter of the treated effluent (80-90 %). Obtained results indicate that the dye mass loading rate can influence the efficiency of dye removal through an MBR. The use of an appropriate biomass concentration significantly improves the MBR performances for an effective textile wastewater treatment. (C) 2020 Institution of Chemical Engineers. Published by Elsevier B.V. All rights reserved.