Removal of organic matter contained in slaughterhouse wastewater using a combination of anaerobic digestion and solar photoelectro-Fenton processes

Here, the mineralization of organic matter present in slaughterhouse wastewater from a Chilean meat company was achieved by a combination of anaerobic digestion followed by the solar photoelectro-Fenton (SPEF) process. The first step was the biological treatment, during which 90% of COD removal was achieved, producing 90 mL of CH₄. Further, the post-biological effluent showed lower color, odor, amount of solids and turbidity but higher conductivity due to an increase in the concentration of NH₄⁺ and NO₃^-. This was followed by different electrochemical advanced oxidation processes (EAOPs): electro-oxidation (EO), electro-Fenton (EF) and SPEF. With SPEF, almost complete mineralization was achieved with a high efficiency. With SPEF, the fast mineralization rate is due to hydroxyl radicals (OH) that are generated in the bulk, on the anode surface, by solar radiation, and most importantly, by the direct photolysis of complexes formed between Fe³⁺ and some organic intermediates. The combination of both processes, biological digestion and SPEF, produces a totally clarified effluent, with a COD removal greater than the separate processes and better than the final effluent from industrial wastewater plants at comparable reaction times.