TECHNOLOGY FOCUS - BIOTECHNOLOGY - Preferred Methods: The enriching and acclimatizing method of heterotrophic nitrobacteria includes adding cultivation wastewater (greater than 3/4) in a container, assuring aeration of cycle water to be greater than 3 mg/L, adjusting pH to 7.5-8.5 using Na2CO3 solution, adjusting salinity to 1.020 by adding plain water, controlling temperature of waste water to 23-27 degrees C, adjusting COD of wastewater to 5-50 mg/L, enriching and acclimatizing the mixture by adding NH4Cl (0.2-2 g/L) each day, and adjusting the concentration of the NH3-N2 to greater than or equal to 0.5 mg/L. The method includes gradually adding NH3-N2 when concentration of the nitrite N2 begins to reduce, gradually adding NH3-N2, and when enriching and acclimatizing ends, NH3-N2 is added at less than or equal to 10 mg/L every day. After 20 days of acclimation, the heterotrophic nitrobacteria can be separated from acclimating liquid if loss of whole N2 happens in the measurement of organic N2. The method includes separating oceanic heterotrophic nitrobacteria from selective culture medium. The selective culture medium is prepared by weighing ammonium sulfate (0.1 or 0.5 g), magnesium sulfate (MgSO4) (0.03 g) or MgSO4 heptahydrate (MgSO4.7H2O) (0.03), Na biphosphate (0.25 g), potassium biphosphate (0.75 g), Na2CO3 (0.5 g), MgSO4 (0.01 g) or MgSO4.4H2O (0.01 g), glucose (0.1 g), peptone (0.1 g), and agaragar powder (16 g), disinfecting water (1000 ml) by mixing the ingredients with water for 20 minutes at 121 or 23-27 degrees C at pH of 7.5-8.5, and culturing the mixture on shaking bed at 140-200 rpm for 24-48 hours. The measuring of the heterotrophic nitrification ability by the liquid ferment includes obtaining solid-culture selecting strains using drawing method in flat panel, taking two circles to inoculate to liquid culture media to culture on the shaking table at 140-200 rpm for 24-48 hours at 23-27 degrees C, measuring NH3-N2 reduction amount, comparing the measured amount with the reference, and determining the strains having heterotrophic nitrification ability if the reducing amount of NH3-N2 is greater than 20%. Preferred Component: The carrier can naturally settle in seawater and can float and flow under the impact of water to remove the aged biological film. Preferred Properties: The carrier has specific surface area of greater than 600 m2/g and specific weight of 1.022-1.030.