Water treatment method and water treatment apparatus

A water treatment apparatus having

• a biological treatment tank for biologically treating a water to be treated containing dissolved ammonia nitrogen,
• a first measurement device which has a first measurement tank and introduces a portion of the water to be treated flowing into the biological treatment tank into the first measurement tank as a first sample liquid, transfers the ammonia nitrogen dissolved in the first sample liquid, under alkaline conditions, into a gas phase of the first measurement tank as ammonia gas, and measures an ammonia gas concentration C1,
• a second measurement step which has a second measurement tank and introduces a portion of a treated water that has undergone biological treatment in the biological treatment tank into the second measurement tank as a second sample liquid, transfers the ammonia nitrogen dissolved in the second sample liquid, under alkaline conditions, into a gas phase of the second measurement tank as ammonia gas, and measures an ammonia gas concentration C2, and
• a control device for controlling operating conditions for the biological treatment in the biological treatment tank based on the ammonia gas concentration C1 and the ammonia gas concentration C2.

A water treatment method having

• a biological treatment step of biologically treating, in a biological treatment tank, a water to be treated containing dissolved ammonia nitrogen,
• a nutrient supply step of supplying a nutrient to the biological treatment tank,
• a flow rate measurement step of measuring a flow rate of the water to be treated flowing into the biological treatment tank,
• a measurement step of introducing a portion of the water to be treated flowing into the biological treatment tank into a measurement tank as a sample liquid, transferring the ammonia nitrogen dissolved in the sample liquid, under alkaline conditions, into a gas phase of the measurement tank as ammonia gas, and measuring an ammonia gas concentration, and
• a control step of controlling an amount supplied of the nutrient based on an ammonia nitrogen concentration in the water to be treated estimated from the ammonia gas concentration, and the flow rate of the water to be treated.

A water treatment apparatus having

• a biological treatment tank for biologically treating a water to be treated containing dissolved ammonia nitrogen,
• a nutrient supply device for supplying a nutrient to the biological treatment tank,
• a measurement device which has a measurement tank and introduces a portion of the water to be treated flowing into the biological treatment tank into the measurement tank as a sample liquid, transfers the ammonia nitrogen dissolved in the sample liquid, under alkaline conditions, into a gas phase of the measurement tank as ammonia gas, and measures an ammonia gas concentration, and
• a control device for controlling an amount supplied of the nutrient based on an ammonia nitrogen concentration in the water to be treated estimated from the ammonia gas concentration, and a flow rate of the water to be treated.