The removal of high concentrations of phenol from saline wastewater using aerobic granular SBR

The treatment of saline wastewater containing phenol is a challenge faced in the application of biological pollution control technologies. Phenol-laden saline wastewater is generated from various industrial and manufacturing activities. The aerobic granular sequencing batch reactor (GSBR) was investigated in this work in order to assess its performance for the degradation and chemical oxygen demand (COD) removal of phenol as the sole substrate from saline wastewater. The effect of inlet concentration (100–2000 mg phenol/L), cycle time (14–24 h), filling cycle time (1–4 h), shock loading, and total dissolved solids (TDS) concentration (3–8%) were evaluated on the performance of a bench scale GSBR seeded with granules containing mixed phenol-degrading consortia acclimatized to salt. The results showed that the investigated reactor could remove more than 99% of phenol from the feed saline wastewater at inlet phenol concentrations of up to 1000 mg/L, total cycle time of 17 h (15.5 h aerating, 1 h filling, and 30 min settling, decanting and idle) and TDS concentrations up to 8%. A high percent of COD removal and phenol mineralization obtained at these operational conditions. The GSBR could also withstand and absorb the strong phenol shock. Furthermore, the granular biomass in the GSBR indicated high quality in terms of sludge settleability. Overall, the results of this work revealed that establishing a granular biomass containing high concentration of active mixed microbial populations in the GSBR system can achieve complete degradation of high concentrations of phenol in saline wastewater. This makes it a very efficient and flexible technology for treating such waste streams in full-scale applications.