This research aimed to examine the effect of contact time on total organic carbon (TOC) removal rates associated with adsorption of pollutants from different olive mill wastewater (OMW) samples onto activated granular activated carbon (GAC). The first sample was a raw OMW that was microfiltered through a 100 µm membrane and the second sample was an OMW’s permeate from a 50 kDa filtration. The TOC removal rate (%) of pollutants from prefiltered OMW increased over time, reaching its peak after 34 h (2040 min). Subsequently, the system reached adsorption equilibrium, corresponding to a removal rate of 60%. Then, it stabilized at this value till the end of adsorption at 48 h (2880 min). TOC removal rates (%) (corresponding to adsorption at different concentrations of GAC) of pollutants permeating 50 kDa also increased over time, reaching their peaks after 2040 minutes. The highest TOC removal rate was around 85%. This study also investigated the kinetics associated with this adsorption. To gain a comprehensive process understanding, pseudo-first-order (PFO) and pseudo-second-order (PSO) were employed as kinetic models. The second-order model best expressed the adsorption process which achieved equilibrium within 34 h.