The Effect of Benzene,Toluene,and o -Xylene on COD Removal in an Aerobic Fluidized Bed Reactor Utilizing Acetic Acid as the Main Carbon Source

Abstract

A laboratory-scale fluidized bed reactor (FBR) model was operated to examine the effect of BTX on the removal of COD in the presence of acetic acid, which was readily degradable. An activated sludge culture was taken from a petrochemical industry wastewater treatment plant and acclimated first to acetic acid (up to 2,000 mg COD/L), and then to BTX (up to 3 mg/L) as a total concentration. Microbial oxygen uptake rates are controlled during the adaptation period. Then this culture is used as inoculum in the FBR unit. The system was initially operated with a total BTX concentration of 6 mg/L, and concentrations of 12 and 18 mg/L, respectively, were tried during an operational period of 42 days, while the theoretically estimated COD concentration (due to the acetic acid in the system) was kept constant, remaining at 2,000 ± 75 mg/L. An organic loading rate of 1.3 kg/m³/day and a hydraulic retention time of 36 h are the fixed operating parameters used during this study. It was seen that the dissolved COD concentrations in the effluent were relatively low and similar for 6 and 12 mg/L influent BTX concentrations. However, the dissolved COD concentration of effluent wastewater increased significantly when the total influent wastewater BTX concentration was 18 mg/L. The BTX concentration of the effluent wastewater was less than 1 mg/L, indicating BTX was accumulated onto the GAC, or it was biodegraded by attached micro-organisms. The experiments, which were carried out under shock loads of BTX at given intervals (with the FBR operating semicontinuously), proved this result with a very low (actually undetectable) effluent wastewater BTX concentration and a tendency to increase the effluent COD concentration caused foam formation in the reactor due to the adverse effect of BTX.