Water treatment method and water treatment device

A water treatment method for treating a water containing organic matter, phosphorus, and a nitrogen component, the method comprising:

• conducting, in a biological treatment device having at least an aerobic tank, an aerobic biological treatment of an inflow water using a sludge containing granules,
• performing a solid-liquid separation such that a mixed liquid of a treated water and sludge in the aerobic tank is separated into the treated water and a concentrated sludge, and
• returning the concentrated sludge obtained during the solid-liquid separating to upstream of the biological treatment device,
• wherein an ammonium nitrogen concentration remaining as a result of a nitrification reaction in the aerobic tank is measured by an ammonium nitrogen concentration measurement device installed in an outflow portion of the aerobic tank, and an aeration amount of an oxygen-containing gas introduced into the aerobic tank is controlled so that the measured ammonium nitrogen concentration is from 0.5 mgN/L to 5 mgN/L, so as to cause a nitrification reaction to occur on surfaces of the granules, and a denitrification reaction to proceed within an interior of the granules,
• wherein the granules are formed in a granule formation tank that is provided by partitioning off a portion of the aerobic tank, and are supplied from the granule formation tank to a portion of the biological treatment device where the aerobic biological treatment is conducted, and
• wherein the aerobic tank is connected directly to a solid-liquid separation device, the solid-liquid separating being conducted in the solid-liquid separation device.

A water treatment device for treating a water containing organic matter, phosphorus, and a nitrogen component, the water treatment device comprising:

• a biological treatment device that contains at least an aerobic tank and an oxygen-containing gas supply unit for supplying an oxygen-containing gas to the aerobic tank, and is configured to conduct an aerobic biological treatment of an inflow water using a sludge containing granules,
• a solid-liquid separation device that is configured to perform a solid-liquid separation of a mixed liquid of a treated water and sludge in the aerobic tank into the treated water and a concentrated sludge,
• a sludge return unit that returns the concentrated sludge obtained in the solid-liquid separation device to upstream of the biological treatment device,
• an ammonium nitrogen concentration measurement unit that includes an ammonium nitrogen concentration measurement device installed in an outflow portion of the aerobic tank that measures an ammonium nitrogen concentration remaining as a result of a nitrification reaction in the aerobic tank, and
• a control unit that is configured to control an aeration amount of the oxygen-containing gas introduced into the aerobic tank so that an ammonium nitrogen concentration measured by the ammonium nitrogen concentration measurement unit is from 0.5 mgN/L to 5 mgN/L, so as to cause a nitrification reaction to occur on surfaces of the granules, and a denitrification reaction to proceed within an interior of the granules,
• wherein the aerobic tank is connected directly to the solid-liquid separation device.