This study examined anaerobic fluidized- bed reactor performance employed to treat brewery waste water in terms of treatment efficiency on COD and BOD5 reduction under different hydraulic retention time (HRT). It employed a fluidized-bed digester, with liquid volumetric flow rate of 1.7 x 10-6m3/s, superficial velocity of 0.0012 m/s and 0.00026m/s which achieved the velocity required to fluidize 20g activated carbon bed of height 0.03m with 0.384 voidage. The pressure drop across the fluidized-bed was calculated to be 1.848 N/m2. The COD and BOD5 concentration reduction efficiencies were monitored .The results obtained indicate that as HRT increases, the concentration of COD and BOD5 initially at 7137.67 COD mg/l and 2177 BOD5 mg/l decreased to final concentration of 1845.92 mg COD/l and 154.17 mg BOD5/l respectively at10h. The COD and BOD5 reduction efficiencies were observed to be 74.1% and 92.9% at the 10h HRT. The experimental data obtained for COD reduction in this work was used for determination of kinetic parameters from modified mixed-flow equation based on Michaelis-Menten’s kinetics and the correlation coefficient was 0.944 .The maximum substrate utilization rate, rmax and the Michaelis-Menten’s constant, KM, were determined to be 301.5 mg COD/l. h and 1345 mg COD/l respectively. Correction factor (F) of 1.1 when applied to the data will fitted simple mixed flow Michaelis Menten kinetic model well. The deviation from typical Michaelis Menten kinetic model can be attributed to acclimatization time required for effective digestion, flow dynamics in the reactor and existence of multi-organism media which would have promoted other side reactions. Organisms identified from the anaerobic digester include clostridium spp, peptococcus anaerobus, bfidobacteriums spp, desulphoribrio spp, corynebacterium spp, lacto. Keywords: Anaerobic decomposition; Brewery wastewater; Fluidized-bed reactor; Modified Michaelis-Menten’s kinetics
