A novel hybrid biofilm reactor consisting of a single unit, where three different processes take place, is presented in this study. The reactor is run under the fill and draw mode (i.e. sequencial batch reactor) and hybrid operation is achieved as four consecutive steps. These steps are "fill", "fluidized bed reaction", "fixed bed reaction", and "down-flow filtering". The pellet particles are used in the reactor for biofilm formation. The performance of the reactor and the best hybrid operation policy (i.e. optimum operation durations for fluidized and fixed bed operations) are determined by observing the amount of removed organic matter (i.e. COD). The results indicated that the total duration of 4-hour cycles including 10 min filling, 30-60 min fluidized bed and 120-150 min fixed bed reaction and 50 min of filtering yields higher efficiency for moderate strength wastewater. The effect of organic loading rate on COD removal rate is investigated as well. Increased COD loadings (i.e. > 0.4 gCOD m(-2)h(-1)) resulted in higher COD concentrations in the effluent (> 100 mgL(-1)) and reduced removal efficiency to 80 percent. However, maximum removal rates are obtained for the organic loads of 0.1-0.3 gCOD m(-2)h(-1) with lower effluent concentrations (< 60 mgL(-1) of COD). These results underline that stringent effluent requirements can be achieved for moderate strength wastewater in shorter detention times for the examined reactor. In addition, calculations derived from the experimental results reveal that the proposed system needs less area (three times small) requirements than those of conventional methods.