Combination of Photo-Fenton and Granular Activated Carbon for the Removal of Microcontaminants from Municipal Wastewater via an Acidic Dye

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.