As the quality of raw water deteriorates, a number of additional treatment techniques have been developed and adapted to water treatment for producing a safe and aesthetically satisfactory drinking water. So, BACFB process as pretreatment in water supply is to be effective to remove dissolved organics. This study performed to find out the effects of HRT and hydraulic characteristics on BACFB reactors in water supply. The flow type in reactor was a high dispersion with complete mixing. As superficial velocity was increased, bed expansion was closed to theoretical values. It was considered that below 30 min HRT could operated to ensure the removal of dissolved organics