AMMONIUM REMOVAL FROM COKING WASTEWATER IN A PILOT-SCALE TWO-STAGE AEROBIC BIOFILM SYSTEM: BIOKINETIC ANALYSIS

A novel four-stage pilot-scale anaerobic/anoxic/oxic/oxic (A(2)/O-2) biofilm process was successfully developed to treat coking wastewater with high ammonium loading. In this study, three different dynamical models including the first-order substrate removal model, the Monod-biological contact oxidation (Monod-BCO) model, and the modified Stover-Kincannon model were particularly applied to analyze kinetics of ammonium removal in a two-step aerobic stage. For the O-1 reactor, all models were appropriate for describing ammonium removal and the correlation coefficients of first-order substrate removal model, BCO model, and modified Stover-Kincannon model were 0.8974, 0.9210, and 0.9726, respectively. The model verification indicated that the modified Stover-Kincannon model was slightly more applicable to predict ammonium removal in the O-1 reactor. It was demonstrated that the maximum removal rate of ammonium was 0.208kg/(m(3).d) by the Stover-Kincannon model. For the O-2 reactor, the modified Stover-Kincannon model turned out to be the best fitting kinetic model for ammonium removal compared to the first-order substrate removal model (R-2=0.1556) and Monod-BCO model (R-2=0.5022). The maximum ammonium conversion rate (Um2-O2) by the modified Stover-Kincannon model was 1.180kg/(m(3).d), while saturation rate constant k(3-O2) was 1.221kg/(m(3).d). Furthermore, the determination coefficient between measured and predicted values obtained by the modified Stover-Kincannon model was quite high (R-2=0.9788) in the O-2 process and a lower average residual square (6.60x10(-6)) was also obtained. The results of kinetic studies by the Stover-Kincannon model can predict ammonia removal efficiency well in two-step aerobic biofilm reactors of a coking wastewater treatment combined system.