Carbonized material has a biological affinity and it is effective for the immobilization of microbes. This study examined the enhancement of biological nitrogen removal in the wastewater treatment by use of carbonized textile as the immobilizing carrier of nitrifying bacteria. Carbonization experiments of cotton and rayon were performed, and rayon carbonized at relatively low temperature was selected as the immobilizing carrier. The performances of microbe adhesion and nitrogen decomposition were examined by using nitrifying bacteria. From these examinations, the carbonization of textile was recognized to be effective for the immobilization of nitrifying bacteria. In the wastewater treatment by using a small reactor and ammonia-rich model wastewater, the ammonia removal was higher for the reactor installed with carbonized textile than for that without it. To examine the conditions of the immobilizing carrier for continuous treatment of wastewater, the flow characteristics of a large rectangular airlift bubble column were measured. Based on the energy balance, the liquid circulation flow rate was analyzed, and the distribution of dissolved oxygen in the column and the fraction of the anaerobic region were estimated. The continuous treatment of wastewater was conducted by using two large columns with and without carbonized textile installed. The BOD removal was unchanged, but the ammonia removal was higher for the reactor with carbonized textile than for that without it.