Concentration apparatus and concentration method

A concentration apparatus comprising:

• a negatively charged membrane that is negatively charged;
• a sample water supply disposed upstream of the negatively charged membrane and operable to supply sample water;
• a first solenoid valve disposed on a flow path from the sample water supply to the negatively charged membrane;
• an acidic solution storage tank disposed upstream of the negatively charged membrane in parallel with the sample water supply and storing an acidic solution;
• a second solenoid valve disposed on a flow path from the acidic solution storage tank to the negatively charged membrane;
• an alkaline solution storage tank disposed upstream of the negatively charged membrane in parallel with the sample water supply and the acidic solution storage tank and storing an alkaline solution;
• a third solenoid valve disposed on a flow path from the alkaline solution storage tank to the negatively charged membrane;
• an outlet disposed downstream of the negatively charged membrane and operable to discharge fluid externally;
• a fourth solenoid valve and a first suction pump each disposed on a flow path from the negatively charged membrane to the outlet;
• a collection container disposed downstream of the negatively charged membrane in parallel with the outlet and in which fluid is collected;
• a fifth solenoid valve disposed on a flow path from the negatively charged membrane to the collection container;
• and
• a controller that controls opening and closing of the first solenoid valve, the second solenoid valve, the third solenoid valve, the fourth solenoid valve, and the fifth solenoid valve,
• wherein
• the controller is operable to execute a sequence of:
• opening the first solenoid valve and the fourth solenoid valve, closing the second solenoid valve, the third solenoid valve, and the fifth solenoid valve, and causing the first suction pump to be driven;
• opening the second solenoid valve and the fourth solenoid valve, closing the first solenoid valve, the third solenoid valve, and the fifth solenoid valve, and causing the first suction pump to be driven;
• and
• opening the third solenoid valve and closing the first solenoid valve, the second solenoid valve, the fourth solenoid valve, and the fifth solenoid valve.