Active management of fluidized beds of activated carbon
The invention relates to a method for treating an aqueous fluid, comprising bringing into contact the aqueous fluid with a fluidised bed of powdered activated carbon, and separating the aqueous fluid from the bed of powdered activated carbon, including a step of managing the fluidised bed of powdered activated carbon. The management step comprises the extraction of a fraction of the fluidised bed of powdered activated carbon in the form of sludge, at least a separation of the sludge extracted in the previous step so as to obtain a fraction having an insoluble index HCl which is higher than that of the sludge before separation by at least 5 percentage points, and a reinjection of said fraction into the fluidised bed of powdered activated carbon.
1. A method for treating an aqueous fluid comprising the contacting of the aqueous fluid with a fluidized bed of powdered activated carbon, coagulated and optionally flocculated, and a gravitational separation of the aqueous fluid from the bed of coagulated powdered activated carbon that is optionally flocculated, said method for treating being characterized in that it comprises a management step of the fluidized bed of coagulated, powdered activated carbon, optionally flocculated, said management step comprising:
(a) an extraction of a fraction of the fluidized bed of coagulated powdered activated carbon, optionally flocculated, in the form of sludge;
(b) at least one separation of the sludge extracted at step (a) so as to obtain a first fraction and second fraction, the first fraction having an HCl-insoluble value higher by at least 5 percentage points than that of the sludge before separation;
(c) a re-injection of the first fraction obtained at step (b) into the fluidized bed of coagulated powdered activated carbon, optionally flocculated,
wherein the contacting of the aqueous fluid with the fluidized bed of powdered activated carbon, coagulated and optionally flocculated, and the separation of the aqueous fluid from the bed of coagulated powdered activated carbon that is optionally flocculated are conducted in a single treatment reactor with powdered activated carbon having up-flow operation, wherein the aqueous fluid containing powdered activated carbon and coagulating agent(s) is fed into the lower part of the treatment reactor, and wherein the first fraction is returned to the bottom of the reactor by means of a pipe or channel.
2. The method according to claim 1 , wherein the first fraction obtained in step (b) has a concentration of suspended solids (SS) at least twice higher than the SS concentration of the sludge before separation.
3. The method according to claim 1 , wherein the separation step (b) is carried out by means of at least one hydrocyclone.
4. The method according to claim 1 , wherein the separation step (b) is performed continuously or periodically.
5. The method according to claim 1 , wherein said first fraction has an HCl value higher by at least 10 percentage points than that of the sludge before separation.
6. The method according to claim 1 , wherein a single separation is carried out in step (b) and the second fraction obtained has a SS concentration at least 1.5 times less than that of the fraction in the form of sludge extracted in step (a).
7. The method according to claim 6 , wherein the second fraction is treated by clarification or flotation upstream of the treatment reactor or removed.