Biological removal characteristics of phenol with filtration bio-reactor

A laboratory scale bio-reactor equipped with a filter module was examined for the separation of activated sludge, where the effluent was withdrawn by mesh filtration. The synthetic wastewater containing phenol was fed into the reactors, and the removal performance was evaluated under the following conditions: 7 or 14 d of HRT, room temperature (ca. 20°C), synthetic wastewater containing 5,000–20,000 mg/L of phenol, 262 mg/L of NH4-N, 43.7 mg/L of PO4-P, maximum phenol loading rate: 1.43 kg/m3/d, feeding the synthetic wastewater for 5 or 10 h (Run-1) or feeding at once (Run-2), and filtration once a day. The reactors maintained high concentrations of MLSS (10,000–15,000 mg/L), and the filtration was carried out stably in a short time. When the synthetic wastewater containing 5,000 mg/L of phenol was fed into the reactor at 7 d of HRT (0.7 kg/m3/d of phenol loading rate), in the operation of Run-1, the removal rates for phenol, NH4-N, and D-TN were above 99.9, 98, and 96%, respectively. Similar results were also obtained in the operation of Run-2. The microbial activity for phenol decomposition was influenced slightly by phenol-MLSS loading rate, but it was significantly affected by the initial phenol concentration in Run-2. The sludge properties such as floc size and content of exocellular polymer affected the filtration performance of this system.