Biodegradation of 4-chlorophenol in an airlift inner loop bioreactor with mixed consortium: effect of HRT, loading rate and biogenic substrate

In the present work, removal of 4-chlorophenol (4-CP) by the mixed microbial consortium was evaluated in an airlift inner loop bioreactor. During the study, the effect of various reactor parameters such as hydraulic retention time (HRT), biogenetic substrate concentration, loading rate, and initial substrate concentration on the removal efficiency of 4-CP was investigated. Bioreactor showed a maximum removal rate of 16.59 mg/L/h at the optimum conditions of 24 h HRT, 400 mg/L initial 4-CP, and 0.2 g/L peptone. The optimum HRT found was 24 h after that the washout occured, and the degradation efficiency almost dropped to 50 % at 18 h HRT. Effect of peptone showed that lower concentration of peptone improves 4-CP removal efficiency of the bioreactor. Also, the mixed consortium had utilized 4-CP as a carbon source, as evidenced by the increasing biomass concentration with 4-CP at constant peptone concentration. The presence of 5-chloro 2-hydroxymuconic semialdehyde in the reactor infers that the mixed consortium has followed the meta-cleavage pathway for 4-CP degradation.