The challenge of microcontaminants (MCs) in wastewater effluent has been addressed by using different technologies, including advanced oxidation processes (AOPs) and adsorption. This work evaluates the benefits and synergies of combining these two processes. The AOPs were photo-Fenton and UV/H₂O₂ operated under natural pH but with different reagents dosages, lamps, and chelating agents. Chelating agents were used at analytical (ethylenediamine-N,N-disuccinic acid and citric acid) and technical grade (citric acid) to simulate scaling-up conditions. The adsorption process was studied via granular activated carbon (GAC) filtration using fresh and regenerated GAC. Four AOP scenarios were selected and coupled with GAC filtration, showing benefits for both processes. AOP treatment time decreased from 10–15 min to 5 min, resulting in a reduction in energy consumption of between 50 and 66%. In the photo-Fenton process, it was possible to work with low reagent dosages (1.5 mg L⁻¹ iron and 20 mg L⁻¹ of H₂O₂). However, the use of UV/H₂O₂ showed close removal, highlighting it as a real alternative. An extension of the GAC lifetime by up to 11 times was obtained in all the scenarios, being higher for regenerated than for fresh GAC. Furthermore, the toxicity and phytotoxicity of the treated wastewater were evaluated, and no acute toxicity or slight variation in the phytotoxicity was observed in the combination of these processes.

Combining photo-Fenton and granular activated carbon (GAC) is an alternative to increase the feasibility of using photo-Fenton in full scale. This work is a preliminary study of its viability at natural pH. Both technologies were applied separately and compared with their combination, GAC filtration instead of batch mode, to achieve an approach close to full scale. The target compound considered in this investigation was indigo carmine as a hydroxyl radicals’ probe. The results show that 80% removal of the target compound could be achieved when 20 min of the photo-Fenton treatment time was applied with the optimal dosing of the reagents (5 mg L⁻¹ of iron and 40 mg L⁻¹ of H2O₂) working at natural conditions and using ethylenediamine-N,N-disuccinic acid as a chelating agent. Two GAC types, fresh GAC and regenerated, were evaluated on Rapid Small-Scale Columns showing similar breakthroughs and close capacity to adsorb the target compound per gram of GAC. Combining the technologies, with photo-Fenton as the first step and GAC as the second, was performed with 5 min of photo-Fenton treatment time. The 80% removal was maintained during 340 and 170 bed volumes for fresh and regenerated GAC, respectively. Aiming to achieve the maximum reduction of irradiation, 75% of the energy consumption was saved compared to the standalone photo-Fenton process, and the GAC life was extended to a maximum of 7 times.