The utility model provides a can low -costly utilize the wastewater treatment apparatus of the stable denitrogenation processing of anaerobic ammonium oxidation method. Wastewater treatment apparatus(1) possess by little biological sludge to contain in the ammoniacal nitrogen of drainage carry on the oxidation ammonia oxidation groove (100) and to the little biological sludge who takes out from ammonia oxidation groove (100) add thermal treatment with heat channel (120). Utilize from the heat of carrying out digestive digestion tank (50) by anaerobism nature microorganism to waste sludge or being arranged in supplying with heat source (80) of being undertaken heating by digestive waste sludge at digestion tank (50) to add thermal treatment to the little biological sludge who takes out from ammonia oxidation groove (100), will through add thermal treatment make the nitrite -oxidizing bacteria activity reducing little biological sludge send ammonia oxidation groove (100) back to, will contain the nitrogen in the ammoniacal nitrogen oxidation one -tenth nitrite of drainage.