Combining fluidized and fixed-film processes in a single biofilm reactor for organic matter removal

In the presented study, organic matter removal performance of various biofilm reactors, that is, fluidized bed, fixed-bed, and hybrid conditions, was investigated. The reactor configurations were run under varying influent chemical oxygen demand (COD) concentrations, that is, 500, 1,000, and 2,000 mgCOD/L, and performance was expressed in terms of COD removal efficiency. The conducted data was analyzed statistically by the Least Significance Test (LSD) and the effectiveness of each reactor configurations was assessed. Significant differences were found between the efficiencies of each reactor configuration. For example, for 500 mg/L influent COD concentration, about 95% of COD was removed in fluidized bed operation, while only 53% of COD was eliminated in a fixed-bed operation. Implementation of hybrid conditions, that is, fluidized+fixed-bed operations was yielded 53, 75, and 84% efficiencies for the 20-min fluidized bed+340-min fixed-bed, 40-min fluidized bed+320-min fixed-bed, and 60-min fluidized bed+300-min fixed-bed operations, respectively. These findings indicated that hybrid conditions can provide equivalent efficiencies to fluidized case if fluidization period can be set properly. In the research, 60-min fluidization and 300-min fixed condition reflected the same efficiencies with fluidized case. These results were also assured by flux calculations. In addition, the efficiencies of each reactor configurations were negatively affected when influent COD concentrations were increased to 1,000 and 2,000 mg/L. Especially for the 2,000 mg/L influent COD concentration, overall removal efficiency was 49% (as an average) in the fixed-bed operation