| 摘要 |
<p>PURPOSE:To hold sludge concentration constant by providing a transmission type photosensor in a circulation path of water to be treated in a sewage treatment tank. CONSTITUTION:A transmission type photosensor S in which both a light projecting face and a light receiving face are opposed is provided in a sewage treatment tank 1 or in a circulation path 7 of water to be treated. Quantity of light of the photosensor S is controlled to the limit of transmission and nontransmission, and a transmission light signal is inputted to a first timer A and also a nontransmission light signal is inputted to a second timer B. The output of the first timer A is inputted to a pump for driving a concentration. sludge reduction mechanism 5 as a low sludge concentration signal, and the output of the second timer B is inputted to a pump for driving a high- concentration sludge drawing-out mechanism 5 as a high-concentration sludge signal. Control of sludge concentration is performed by the distance between the light projection face and the light receiving face of the photosensor S, quantity of light and time setting. Thereby automation, and labor saving are performed.</p> |
