A wastewater treatment apparatus comprises a nitrogen-containing dye containing wastewater inlet connected to an obligatory anaerobic tank to bring wastewater containing a nitrogen-containing dye into contact with sulfate-reducing bacteria under obligatory anaerobic conditions, a nitrification tank to bring the wastewater into contact with nitrifying bacteria under aerobic conditions, and a denitrification tank to bring the wastewater into contact with the denitrifying bacteria under anaerobic conditions.