Method and a device for biologically treating a contaminated liquid feedstock including a dispersible and digestible organic liquid phase such as a toxic oil or solvent

A method of biologically treating a toxic liquid feedstock comprising an organic liquid phase that is dispersible and digestible, such as a toxic oil or solvent, the method being characterized by the successive steps consisting in:

• a) feeding a first vessel (100) with the liquid feedstock for treatment, the first vessel containing an aqueous phase and a first bacterial population;
• b) dissolving the liquid feedstock for treatment in the first vessel by enzymatic hydrolysis using the first bacterial population;
• c) drawing off a first reaction liquid product from the first vessel;
• d) filtering from the first reaction product the biomass contained therein, thereby obtaining a first effluent;
• e) feeding a second vessel (200) with the first effluent, the second vessel containing an aqueous phase and a second bacterial population that is different from the first bacterial population;
• f) biodegrading the first effluent in the second vessel by biological digestion using the second bacterial population;
• g) drawing off a second liquid reaction product from the second vessel;
• h) filtering from the second reaction product the biomass contained therein in order to obtain a second effluent;
• i) adjusting the bacterial concentration in the second vessel by extracting the surplus biomass;
• j) feeding a third vessel (300) with the second effluent, the third vessel containing an aqueous phase and a third bacterial population that is different from the first and second bacterial populations;
• k) reducing the residual bacterial components of the second effluent in the third vessel by bacterial action using the third bacterial population;
• l) drawing off a third liquid reaction product from the third vessel;
• and
• m) filtering from the third reaction product the biomass contained therein in order to obtain a third effluent;
• the third effluent constituting a final liquid effluent (EFF/N) that is essentially non-organic, and the separated biomass constituting an ultimate organic waste (DU) of reduced volume.