NOVELTY - Removal of nitrogen and chemical oxygen demand (COD) component from ammoniacal liquor involves using denitrifying bacterium in ammoniacal liquor activated sludge and COD component in ammoniacal liquor at anaerobic tank, performing decomposition and denitrification of COD component by reducing nitrite nitrogen in circulation liquid to nitrogen gas, using biological nitrification-denitrogenation which liquid feeds the treated water of anaerobic tank to aerobic tank, and performing COD component addition where biodegradation to anaerobic tank is possible.    USE - Removal of nitrogen and COD component from ammoniacal liquor.    ADVANTAGE - The efficiency of removal by biological treatment of high concentration ammonia nitrogen contained in ammoniacal liquor and COD component is increased.    DETAILED DESCRIPTION - Removal of nitrogen and chemical oxygen demand (COD) component from ammoniacal liquor involves circulating anaerobic tank through nitrite nitrogen containing liquid while oxidizing ammonia nitrogen in ammoniacal liquor to produce in aerobic tank using ammonium oxidizing bacteria in ammoniacal liquor activated sludge from coking plant and producing nitrite nitrogen, using denitrifying bacterium in ammoniacal liquor activated sludge and COD component in ammoniacal liquor at anaerobic tank, performing decomposition and denitrification of COD component by reducing nitrite nitrogen in circulation liquid to nitrogen gas, using biological nitrification-denitrogenation which liquid feeds the treated water of anaerobic tank to aerobic tank, estimating nitrite nitrogen production amount in aerobic tank from ammonia nitrogen concentration and alkalinity in ammoniacal liquor while requiring COD component concentration in ammoniacal liquor where biodegradation by denitrifying bacterium is possible and estimating amount of nitrite nitrogens where denitrification in anaerobic tank is possible from COD component concentration, determining necessity for addition of COD component where biodegradation to anaerobic tank from 2 estimator is possible and necessity for pH control by aerobic tank, performing COD component addition where biodegradation to anaerobic tank is possible which selects processing which does not perform pH control by aerobic tank or carries out pH control by aerobic tank, and removing nitrogen in ammoniacal liquor by reaction with COD component.