Startup kinetics of aerobic Moving Bed Biofilm Reactors for phenolic wastewater treatment by mesophilic bacteria

Phenol and its derivatives are toxic chemicals widely used in industries like plastics, coal tar resins, coking, and medicine. Classified as one of 129 essential pollutants by NPRI and USEPA, phenol requires proper wastewater treatment to prevent environmental and health hazards. This research investigates the startup kinetics of a Moving Bed Biofilm Reactor (MBBR) designed for the treatment of synthetic wastewater including phenol and glucose as principal substrates. The reactor operated at an 18-hour hydraulic retention time (HRT), an organic loading rate (OLR) of 0.0013 kg COD/L per day, and a pH of 7–9, with a constant influent COD of 1000 ± 20 mg/L. Biomass was first acclimated to glucose and then gradually to phenol over five phases spanning seven months and 22 days. Using the Monod model, key biokinetic parameters at full phenol concentration were determined: Ks = 47.62 mg/L, k = 0.0485 mgCOD/mgVss·days, Y = 0.336 mgVss/mgCOD, kd = −0.024 days⁻¹, and μmax = 0.016 days⁻¹. The highest COD removal efficiency and biomass concentration were 92 % and 7.92 mg/L, respectively. The reactor reached pseudo-steady state in 41 days. Phase 5 showed a good model fit (R² = 0.88–0.90), confirming the reactor's efficiency for industrial-scale phenolic wastewater treatment. The significant R² values of 0.88 and 0.90 for the Monod model in final stage indicate that the kinetic parameters derived are well aligned with the experimental data, effectively depicting microbial growth and substrate utilisation. It also demonstrates the reactor's effectiveness for the industrial-scale treatment of phenolic waste.