Kinetic Modeling and Parameter Estimation for an Activated Sludge Unit Treating 2,4 Dichlorophenol Containing Synthetic Wastewater

A mathematical model was developed for an activated sludge unit treating 2,4 dichlorophenol (DCP) containing synthetic wastewater. The model included DCP inhibition on COD and DCP removal. Experimental data obtained at different hydraulic residence times (HRT = 5–40 h) and solids retention times (SRT = 5–30 days) were used to estimate the kinetic and inhibition constants for COD and DCP removal rates. The specific rate constant (k), saturation constant (K_s ) and DCP inhibition constant (K_DCP ) for COD oxidation were found to be 0.87 days⁻¹, 22 mg L⁻¹, and 490 mg L⁻¹, respectively. A similar model was used for DCP oxidation in the activated sludge unit and the constants were found to be k´ = 1.87 days⁻¹, K´_s = 39 mg L⁻¹, K´_DCP = 79 mg L⁻¹, and KI,DCP = 3.26 mg L⁻¹. Increases in death rate constant (b) because of DCP inhibition was also quantified and the inhibition constants were determined for both COD and DCP removals. DCP inhibition on DCP removal kinetics was found to be more pronounced compared to COD removal. Model predictions with the estimated kinetic constants were in good agreement with the experimental data.