Phenol biodegradation and simultaneous nitrogen removal using a carbon fiber felt biofilm reactor

Phenol biodegradation and its effect on the biological nitrogen removal were studied in a biofilm reactor (15 L) packed with carbon fiber felt carriers. Meanwhile, the effects of the effluent internal recirculation ratios (0, 100% and 200%) and the air flow rates (0.42, 0.83, 1.46, 2.08 and 3.33 L/min) on the performance of system were tested. The system exhibited an excellent capacity for simultaneous phenol biodegradation and biological nitrogen removal without effluent internal recirculation when the influent phenol concentration was as high as 1,000 mg/L (organic loading rate of 9.54 kg COD/(m³ d)) and the ammonia loading rates of 0.20, 0.32 and 0.40 kg NH₄⁺-N/(m³ d) respectively). Nitrification process was inhibited at the influent phenol concentration of 1,200–1,300 mg/L with average ammonia removal efficiency of 26.9%. The nitrifiers activity could be recovered in the perfect performance of system for phenol biodegradation. However, denitrification was not affected by the process of phenol biodegradation. In the air flow rates of 1.46–2.08 L/min, the system manifested stable operation for phenol elimination and nitrogen removal. Dissolved oxygen (DO) distributions in carbon fiber felt biofilm descended gradually from the external to the center of the carrier in all air flow rates.