Activated carbon from water treatment sludge (WASC) was employed as adsorbent material to remove the anti-inflammatory Nimesulide (NM) from aqueous solutions. NM adsorption was performed in batch and fixed-bed systems, evaluating pH, adsorbent dosage, adsorption kinetics, equilibrium isotherm, continuous adsorption, and simulated effluents. The kinetic data were best fitted to the Elovich model and Intraparticle diffusion reaching the equilibrium at 120 min. Langmuir model presented a better description of the equilibrium data with the maximum adsorption capacity (qmax) of 274.99 mg g− 1 from NM adsorption by WASC. The adsorbent was tested in two simulated hospital effluents and proved to be an excellent adsorbent for removing NM from an aqueous solution with the presence of salts, sugars, and other inorganics. Finally, WASC was applied in fixed-bed NM adsorption obtaining the adsorption capacity of 217.28 mg g− 1.