Anaerobic Biogranulation Using Phenol as the Sole Carbon Source

The granulation process was extensively examined using phenol as sole carbon source in a 2‐L laboratory upflow anaerobic sludge blanket (UASB) reactor. The study was conducted mesophilically at 35 °C. Anaerobically digested sludge was used as seed after a 14‐day activation period with glucose feed. Massive initial granules were developed after 3 months of startup, grew at an accelerated pace for 6 months, then became fully grown. The granulation process can be broken into three phases: acclimation, granulation, and maturation. However, granulation with phenol proceeded more slowly than it did in UASB reactors fed with readily biodegradable carbohydrates studied previously. The granular sludge cultivated had a median diameter of 1.8 mm, phenol‐degrading activity of 0.65 g chemical oxygen demand (COD)/g volatile suspended solids (VSS)·d, and a sludge volume index of 14 mL/g. Phenol COD removal efficiency of 86% was achieved when the reactor was operating at an influent phenol concentration of 1260 mg/L (corresponding to 3000 mg COD/L), hydraulic retention time of 12 hours, and volumetric loading rate of 6 g COD/L·d. However, the lower‐than‐expected phenol COD removal efficiency could be attributed to inhibition by the high influent phenol concentration or loading. The batch test demonstrated that the sludge methanogenic activity was reduced by 52 and 75% at phenol concentrations of 420 and 840 mg/L, respectively.