Thermophilic biodegradation of phenol-catechol wastewater by a microbial consortium: kinetic modeling and sequencing...

Aerobic biodegradation of mixed phenolic wastewater containing phenol and catechol was investigated under thermophilic conditions to integrate biodegradation kinetics with practical sequencing batch reactor (SBR) design. A thermotolerant microbial consortium was used to evaluate treatment performance, parameter optimization, substrate inhibition kinetics, and reactor-scale translation. Six physicochemical parameters - temperature, pH, incubation time, medium volume, inoculum size, and initial substrate concentration - were optimized to maximize removal efficiency. Under optimal conditions (45 °C, pH 8.5, 48 h, 600 mL working volume, 12% inoculum, and 1000 mg L⁻¹ total substrate), 99.9% degradation of the phenol-catechol mixture was achieved within 48 h.The biodegradation kinetics followed the Haldane substrate inhibition model, yielding kinetic parameters of μ_m = 0.061 h⁻¹, K_s = 38.65 mg L^-1, K_i = 138.24 mg L^-1, and Y_x/s = 0.0035 OD₆₀₀·L·mg^-1, with strong model agreement (R² > 0.99). Using these parameters, a pilot-scale SBR (2.2 m³ working volume) was designed with a 48 h reaction cycle, aeration rate of 1 vvm, and power input of 0.05 W L^-1, achieving 95-98% substrate removal per cycle under thermophilic and alkaline conditions.Overall, this study demonstrates the direct integration of mixed-substrate biodegradation kinetics with reactor-scale process design, bridging laboratory-scale modelling and applied wastewater treatment engineering for high-strength phenolic effluents.