COAGULATION-SETTLED ACTIVATED SLUDGE TREATMENT SYSTEM AND COAGULATION-SETTLED ACTIVATED SLUDGE TREATMENT METHOD

摘要

PROBLEM TO BE SOLVED: To reduce running cost by allowing an early stable operation and reducing the amount of coagulant.SOLUTION: A second inorganic coagulant is added to a part of metal component-containing primary coagulated sludge, that is sludge returned from a settlement tank 3, to generate metal component-containing secondary coagulated sludge higher in metal ratio than the metal component-containing primary coagulated sludge by an electrochemical reaction of a metal component of the second inorganic coagulant with the metal component-containing primary coagulated sludge, and the metal component-containing secondary coagulated sludge is returned to between the downstream side of a biological reactor 1 and the upstream side including the settlement tank 3. In this way, a part of metal component-containing coagulated sludge is subjected to the electrochemical reaction with the metal component of the second inorganic coagulant without being returned to the biological reactor 1, and this process is repeated, whereby, compared with a process by returning all of the returned sludge to the biological reactor 1, the accumulation of the metal component to the sludge is efficiently promoted to reduce the period until the metal ratio reaches an equilibrium value, and the amount of the inorganic coagulant is reduced for a reduced amount of the period.