A submerged biological fixed-film reactor packed with plastic corrugated plates was employed to treat a wastewater of 100-400 mg NH4+-N/l and 80-130 mg COD/l. Nitrification and COD removal occurred in the reactor simultaneously. The kinetics of ammonium inhibition was studied, and used to control the bioreactor with the optimum condition. This operation strategy of kinetic control was able to reduce the duration of the acclimation of nitrifying bacteria in the reactor, and to enhance the removal of ammonium up to 95-98 %. The flow mode of indirect aeration in the reactor was able to maintain the suspended solid in the effluent below 4 mg/l without biofilm sloughing-off throughout the 300 operation days. In addition, the kinetic control and indirect aeration strategy of operation were able to obtain stable and low concentrations of COD, ammonium and nitrite in the effluent, and a high biomass of 14 g VSS/l in the reactor, when the influent loading of ammonium was up to 0.74 kg NH4+-N/m3-day associated with the medium surface loading of 10.4 g NH4+-N/m2-day.

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