A sorbent (Organosorb) is used in the wastewater purification from organic contaminants, here simulated by tetradecane. A short hydrodynamic treatment in a rather intense hydrodynamic field (G>10(3)) (called ultraflocculation) is applied to the sorbent suspension to which a flocculant is added. The efficiency of removal of the sorbent is studied. The sorbent concentration, the flocculant concentration, the treatment time, the organic pollutant (which has to be sorbed by the sorbent), the detergent (used for the emulsification of the pollutant), the pH and the calcium concentration of the water all influence the flocculation efficiency (E) of the sorbent particles. For each set of these parameters there exists an optimum intensity of the hydrodynamic treatment at which maximum flocculation efficiency is reached. An increase in the optimum intensity of the hydrodynamic field corresponds to an increased floc break-up, and consequently a lower maximum flocculation efficiency.