| 摘要 |
PROBLEM TO BE SOLVED: To make amount of addition of a dehydrating agent appropriate so as to perform effective dehydration by making a dehydrated filtrate into a measuring portion, measuring generating frequency of Karman vortex induced in the dehydrated filtrate and controlling the amount of chemical injection through a chemical injection pump according to a value thus detected. SOLUTION: A dehydrating agent is added to sludge by a chemical injection pump 1 and in order to subject the filtrate to dehydrating treatment by using a sludge dehydrating device 2, dehydrated filtrate discharged from the sludge dehydrating device 2 is guided into a measuring section 3 so as to detect generating frequency of Karman vortex by using a vortex sensor, and according to a value thus detected, an appropriate additional amount of the dehydrating agent is determined by a chemical injection control panel 4 and a control signal is outputted to a driving device 5 of the chemical injection pump 1 so as to adjust the additional amount of the dehydrating agent. For the purpose that the dehydrated filtrate is made to flow through the measuring section 3 at a constant flow rate, a specified headδH is provided between a filtrate inlet pipe to the measuring section 3 and a dehydrated filtrate outlet pipe from the measuring section 3, and the filtrate is made to flow through the measuring section 3 at a specified flow rate according to the headδH.
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