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

Abstract

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.