| 摘要 |
<p>PURPOSE:To pertinently control the withdrawal of excess sludge and balance between an amount of sludge in an aerating cell and that in a precipitating pool, by properly increasing or decreasing the preset value of an entire amount of retained sludge and the preset value of the ratio of a flow amount of returned sludge to that of filthy water in response to the increase or decrease of a flow amount of filthy water flowing into the aerating cell. CONSTITUTION:Signals from a flow meter 1 for filthy water, a turbidometer 2, a flow meter 6 for returned sludge, a densitometer 7 for returned sludge and a flow meter 11 for withdrawn excess sludge are fed to an electronic computer 12 which calculates an entire amount W of retained sludge and the ratio R of returning sludge, i.e. the ratio of a flow amount QR of returned sludge to a flow amount QS of filthy water. The amount W is fed to the first controller 13, while the ratio R is fed to the second controller 14. These deviations from preset values are calculated by the controllers 13, 14. Hence, when the amount of filthy water to the aerating cell 3 is increased, a controller 16 for an upper level is operated to enhance the preset value of the amount W and to lower the preset value of the ratio R. When said amount is decreased, the controller 16 is conversely operated. Excess sludge is discharged from a pipe line F through a convertor 18 and a setting instrument 20, and the amount of sludge to be returned is controlled through a convertor 19 and a setting instrument 21.</p> |
