Continuous Phenol Biodegradation in a Bioreactor at Upflow Packed Bed by Mixed Microbial Culture

This study aims to evaluate the performance of a bioreactor at an upflow packed bed with synthetic wastewater containing phenol under continuous operation. The used microorganism was formed by a mixed culture isolated from a wastewater treatment plant. The mean residence time (t_m = 3.92 h) in the bioreactor was obtained experimentally by following the tracer NaCl 0.5 M concentration in a continuous effluent stream. For the first time, we calculated the superficial velocities of liquid (u_L) and gas (u_G) in a three-phase medium (air-water-sand) in the absence of biomass; these velocities vary from 5.40 × 10^–3 to 5.84 × 10^–3 and from 0.36 × 10^–3 to 3.67 × 10^–3 m/s, respectively. Afterwards, the effects of airflow (AF = 10, 20, and 30 L/h), liquid flow rates (LF = 3, 5, and 9 mL/min), and initial phenol concentration (C₀ = 100, 200, 300, 500, and 700 mg/L) on the biodegradation rate of phenol were studied. The results indicate that the rate of continuous biodegradation increases with the initial phenol concentration and decreases both with the AF and LF rates. The biofilm concentration uniformly increases with increasing the height of the sand bed. The process in the continuous model also contributed to a high elimination efficiency of 100%.