Performance of the Facultative Stabilization Pond in Removing Phenol from Oil Refinery Effluent

Phenol is a highly toxic aromatic compound discharged into the environment through industrial effluents. The natural biological treatment process has been widely used as one of the most feasible, eco-friendly, and cost-effective options for the treatment of pollutants such as phenol. The objective of the present experimental-analytical study was to evaluate the performance of the facultative stabilization pond in removing phenol and other organic compounds from oil refinery effluents. For the purposes of this study, a pilot-scale anaerobic stabilization pond 1.2×0.6×0.55 m in size was constructed of fiberglass sheets 6 mm in thickness. The experiment was run with a hydraulic retention time of 10 days and a hydraulic loading rate of 43.5 l/d. The organic loading rate for the facultative pond was 150 kg/h.day. Samples were taken after pond operation and seeding when the pond reached its biological stability. Depending on phenol removal levels in the anaerobic stabilization pond, initial phenol concentrations at the inlet to the facultative pond were assumed to be 0-28, 30-80, 90-130, and 150-200 under warm conditions and 100-140, and 200b-260 mg/l in cool conditions. For each sample, the parameters NH3, PO4, and Phenol were measured using the Varian spectrophotometer (model UV-120-02) at the wavelengths of 425, 690, 500 nm, respectively. TCOD, SCOD, TBOD, SBOD, pH, and ORP were also measured according to the standard methods of water and wastewater. The results showed that phenol removal efficiency of the facultative pond was 71.8% for warm temperatures and 14.66% for cool temperatures. It was also found that temperature and phenol concentration significantly affected the performance of the pond. Moreover, its performance was observed to enhance with reducing phenol concentration and increasing temperature (p<0.001). Maximum phenol removal efficiency of the system was recorded at 71.8% for warm temperatures and a low phenol concentration of 0–28 mg/l while its minimum of 14.66% was recorded at a high phenol concentration of 200-260 mg/l under cold weather conditions. Based on the results obtained, it may be concluded that the pilot-scale facultative pond has a high performance in removing organic compounds with different concentrations of phenol under warm weather conditions.