Methylene blue degradation by the UV/TiO 2 and UV/TiO 2 /H 2 O 2 photocatalysis in a suspended photocatalytic reactor coupled with a microfiltration (MF) module is described. The kinetics of methylene blue degradation, cake layer formation on the membrane surface, and the energy consumption of the system are evaluated and discussed. In addition, cost estimation of the treatment of methylene blue by different processes is implemented. The investment and operating costs of the photocatalytic membrane reactors are calculated and compared with the UV systems and UV/TiO 2 -MF.