Organic wastewater treatment device and organic wastewater treatment method

A method for treating organic wastewater, comprising:

• providing, in a biological treatment tank, a whole floor aeration section, a flow path narrowing section, and a solid-liquid separation section from below toward above, the biological treatment tank storing activated sludge therein;
• in the whole floor aeration section, treating the activated sludge by performing overall-aeration of a liquid to be treated;
• in the flow path narrowing section, restricting an upward movement of the activated sludge by narrowing a cross-sectional area of a flow path from the whole floor aeration section toward the solid-liquid separation section in the biological treatment tank so as to combine air bubbles which aerate the liquid in the whole floor aeration section, and discharging a portion of the activated sludge from the whole floor aeration section and the combined air bubbles into the solid-liquid separation section thereabove;
• and
• cleaning a surface of a membrane of the membrane separation device which is immersed in the liquid to be treated with the air bubbles discharged from the flow path narrowing section and extracting an effluent liquid passing through the membrane as a treated liquid.

An organic wastewater treatment apparatus, comprising:

• an anaerobic tank;
• a denitrification tank;
• an aerobic tank;
• in the anaerobic tank,
• a first aeration section configured to perform whole floor aeration with a first aerator disposed on a bottom portion of the aerobic tank or in a vicinity of the bottom portion;
• a second aeration section formed above the first aeration section and provided with a membrane separation device immersed in activated sludge;
• and
• a flow path narrowing section formed between the first aeration section and the second aeration section so as to vertically partition the first aeration section and the second aeration section;
• a first flow passageway configured to transfer a liquid to be treated from the anaerobic tank to which untreated water is supplied to the first aeration section in the aerobic tank;
• a second flow passageway configured to transfer the liquid to be treated from the first aeration section in the aerobic tank to the denitrification tank;
• and
• a third flow passageway configured to transfer the liquid to be treated from the denitrification tank to the second aeration section in the aerobic tank,
• wherein the flow path narrowing section includes a flow path narrowing device configured to narrow a cross-sectional area of a flow path from the first aeration section to the second aeration section in the aerobic tank so as to combine air bubbles discharged from the first aerator in the first aeration section with each other and discharge the combined air bubbles under the membrane separation device in the second aeration section, while the liquid to be treated is transferred from the second aeration section to the first aeration section in the aerobic tank.

An organic wastewater treatment apparatus, comprising:

• an anaerobic tank;
• a denitrification tank;
• an aerobic tank;
• in the aerobic tank,
• a first aeration section configured to perform whole floor aeration with a first aerator disposed on a bottom portion of the aerobic tank or in a vicinity of the bottom portion;
• a second aeration section formed above the first aeration section and provided with a membrane separation device immersed in activated sludge;
• and
• a separation wall formed between the first aeration section and the second aeration section so as to vertically separate the first aeration section and the second aeration section;
• a first flow passageway configured to transfer a liquid to be treated from the anaerobic tank to which an untreated water is supplied to the first aeration section in the aerobic tank;
• a second flow passageway configured to transfer the liquid to be treated from the first aeration section in the aerobic tank to the denitrification tank;
• a third flow passageway configured to transfer the liquid to be treated from the denitrification tank to the second aeration section in the aerobic tank;
• a second aerator configured to transfer air bubbles which are discharged from the first aerator and blocked by the separation wall into the second aeration section and discharge the air babbles under the membrane separation device;
• and
• a sludge transfer passageway configured to transfer the liquid to be treated from the second aeration section to the first aeration section in the aerobic tank to the second aeration section.