NOVELTY - Method for removing an organic substance and nitrogen from sample liquid containing an organic substance and nitrogen, involves using an anaerobic digestion treatment tank having first layer for accommodating microorganisms for anaerobic digestion treatment and second layer for accommodating autotrophic denitrifying microorganisms, and the process involves contacting sample liquid with first layer and decomposing organic substance, further contacting with second layer and carrying out denitrification.    USE - The method is useful for removing organic substance and nitrogen from sample liquid containing organic substance and nitrogen (claimed). The sample liquid includes organic wastewater, beer industrial wastewater, night soil wastewater, domestic wastewater including river water, lake water, marshes and seawater.    ADVANTAGE - The method effectively removes organic substance and nitrogen using separate and compartmentalized reaction tank by simple and inexpensive process.    DETAILED DESCRIPTION - Method for removing an organic substance and nitrogen from sample liquid containing an organic substance and nitrogen, involves using an anaerobic digestion treatment tank having first layer for accommodating microorganisms for anaerobic digestion treatment and second layer for accommodating autotrophic denitrifying microorganisms, and the process involves contacting sample liquid with first layer and decomposing organic substance, further contacting with second layer and carrying out denitrification. The decomposition and denitrification processes are performed one or more times. INDEPENDENT CLAIMS are included for the following:    (1) granule accommodating microorganisms, comprising microorganisms localized on surface layer for anaerobic treatment and autotrophic denitrifying microorganisms localized in inner layer;    (2) solution for acclimatization, comprising lactic acid or propionic acid, ammonia nitrogen, and nitrite nitrogen; and    (3) apparatus for removing organic substance and nitrogen from sample liquid containing nitrogen and organic substance, has anaerobic treatment tank (1) having first layer for accommodating microorganisms for anaerobic treatment, and second layer for accommodating autotrophic denitrifying microorganisms.    DESCRIPTION OF DRAWING(S) - The drawing shows a schematic view of the apparatus for removing nitrogen and organic substance from sample liquid.    Anaerobic treatment tank (1)    Methane-fermentation granule (2)    Sample liquid inlet (4)    Circulation pump (6)    Diffuser (8)