Abstract: A method for treating fluid, notably water, includes a renewal step in order to recover the adsorption capacities of an adsorbent bed, including the extraction of a sample of adsorbent from the adsorbent bed, the determination of a target mean age of the extracted adsorbent sample, in particular by the rejuvenation of at least one portion of the extracted adsorbent sample, at which target mean age the extracted adsorbent has a real abatement of pollutants corresponding to a previously set abatement objective, the rejuvenation of the adsorbent bed to the predetermined target mean age. The method makes it possible to improve the treatment of a fluid by adsorption, and notably to take into account the new contaminants. The disclosure also relates to a plant for treatment according to the proposed method.