Water treatment apparatus with circulating flow path and water treatment method using the same

A water treatment apparatus comprising:

• a cohesive agent input device configured to input a cohesive agent to raw water;
• a membrane filtering device including:
• an inlet configured to allow raw water including the cohesive agent therein to be introduced therethrough;
• a water treatment discharge opening configured to discharge treatment water to be discharged therethrough;
• and
• a raw water discharge opening configured to allow a partial amount of water which is not discharged as treatment water to be discharged therethrough;
• a raw water pump configured to transfer raw water including the cohesive agent therein to the membrane filtering device;
• a water supply flow path connecting a discharge side of the raw water pump to the inlet of the membrane filtering device;
• a circulation flow path connecting the raw water discharge opening of the membrane filtering device to a portion of the water supply flow path downstream of the raw water pump to supply the partial amount of water which is not discharged as treatment water downstream of the raw water pump;
• a positive displacement pump provided in the circulation flow path to transfer discharged raw water to the water supply flow path;
• at least one baffle formed to extend from an inner wall surface of the water supply flow path, and disposed at at least one of a right angle and a slanting angle with respect to a flow direction in the water supply flow path;
• and
• a valve installed at the water supply flow path to adjust an opening degree of the water supply flow path, and disposed downstream of the raw water pump to adjust a flow rate of raw water together with the baffle.