A laboratory-scale powdered activated carbon treatment (PACT) process was conducted to treat the synthetic dye wastewater containing reactive brilliant blue KN-R (RBB). The pore structures of the PAC and molecular structure of the RBB were analysed. The influences of the biomass concentration and the PAC dosage on RBB removal were investigated in an activated sludge system. In addition, kinetic studies based on four fundamental models were investigated. Furthermore, theories about the microscopic dynamic interaction process of PACT were studied. A schematic process of the interaction between activated carbon and microorganisms in a PACT process was proposed. It was concluded that the enhanced treatment of dye wastewater by the PAC in activated sludge process was due to the immobilized microorganisms on the PAC and the bio-regeneration process.