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 thetreatment performance were investigated through systematic experiments in a three-phase biologicalfluidized bed rector with mature biofilm cultivated on synthetic porous particles made of poly(MA-Vac-MMA). Synthetic wastewater consisted glucose, NH_3Cl, KH_2PO_4 and modestly additionalnutrient salts was applied in the experiments. The results indicated that the initial COD and NH_3-Nconcentrations as well as the COD/NH_3-N ratio in the wastewater had impacts on their removals. Theoptimal treatment performances were gained with COD of 700 mg/L, NH_3-N of 25 mg/L and theCOD/NH_3-N ratio of 100/4～100/3 in the raw wastewater, respectively. The variations of air flow rateaffected both the dissolved oxygen concentration in the reactor and the shear force on the surface ofthe biofilm-coated particles, and thus, there existed an optimal air flow rate at which the mosteffective treatment was achieved. It was also found that the favorable range of temperature and pHfor the biodegradation process were 20～25°C and 6～8 respectively, and beyond which the treatmentperformance would be obviously inhibited. Meanwhile, the semi-continuous experiments wereconducted to study the dynamic behaviors of COD and NH_3-N removals in the reactor, and theresponse curves showed that the wastewater contained non-biodegradable contents. Hence, based onthe Michaelis-Menten equation, a kinetic model considering the non-biodegradable contents in thewastewater was proposed to describe the biodegradation process of COD and NH_3-N in the reactor.With the experimental plots, the kinetic parameters were estimated using 4th-order Runge-Kuttamethod combined with simplex method, and the simulated curve of the proposed model showed abetter fit to the actual response plots than the Michaelis-Menten equation did. It confirmed therationality of introducing the substrate inhibiting mechanism caused by the non-biodegradablecontents in the wastewater.