Biodegradation of 2,4-dichlorophenol in Packed-Bed Biofilm Reactor: Effect of Hydraulic Retention Time, Biogenic Substrate, and Loading Rate.

  The removal of 2,4-dichlorophenol (2,4-DCP) by a pure culture of Bacillus endophyticus strain immobilized on ceramic balls was studied in a packed bed biofilm reactor (PBBR). The biodegradation of 2,4-DCP was studied in fed-batch and continuous mode and the effect of different parameters such as hydraulic retention time (HRT), biogenetic substrate concentration, and loading rate on the removal of 2,4-DCP were evaluated. Field emission scanning electron microscope (FESEM) results established the biofilm formation on the ceramic beads. The maximum volumetric removal rate found to be 127.2 mg/L·d at loading rate of 172.8 mg/L·d with 73.6% degradation (12.5 hours of HRT, 90 mg/L of 2,4-DCP, 0.2 g/L of peptone). The bioreactor showed more than 98% removal of 2,4-DCP at loading rate of 115.2 mg/L·d at 12.5 hours of HRT and 0.2 g/L of peptone. Effect of peptone showed that lower peptone concentration increases the removal efficiency; however, some peptone is necessary to maintain the 2,4-DCP removal efficiency.