Experimental study of the operating parameters and biodegradation kinetic model for wastewater treatment in a biological fluidized bed reactor

摘要

The effects of the wastewater contents, air supply, reaction temperature and pH on the treatment performance were investigated through systematic experiments in a three-phase biological fluidized bed rector with mature biofilm cultivated on synthetic porous particles made of poly (MA-VAc-MMA). Synthetic wastewater consisted glucose, NH3Cl, KH2PO4 and modestly additional nutrient salts was applied in the experiments. The results indicated that the initial COD and NH3-N concentrations as well as the COD/NH3-N ratio in the wastewater had impacts on their removals. The optimal treatment performances were gained with COD of 700 mg/L, NH3-N of 25 mg/L and the COD/NH3-N ratio of 100/4～100/3 in the raw wastewater, respectively. The variations of air flow rate affected both the dissolved oxygen concentration in the reactor and the shear force on the surface of the biofilm-coated particles, and thus, there existed an optimal air flow rate at which the most effective treatment was achieved. It was also found that the favorable range of temperature and pH for the biodegradation process were 20～25°C and 6～8 respectively, and beyond which the treatment performance would be obviously inhibited. Meanwhile, the semi-continuous experiments were conducted to study the dynamic behaviors of COD and NH3-N removals in the reactor, and the response curves showed that the wastewater contained non-biodegradable contents. Hence, based on the Michaelis-Menten equation, a kinetic model considering the non-biodegradable contents in the wastewater was proposed to describe the biodegradation process of COD and NH3-N in the reactor. With the experimental plots, the kinetic parameters were estimated using 4th-order Runge-Kutta method combined with simplex method, and the simulated curve of the proposed model showed a better fit to the actual response plots than the Michaelis-Menten equation did. It confirmed the rationality of introducing the substrate inhibiting mechanism caused by the non-biodegradable contents in the wastewater.