Advanced oxidation processes for coffee processing wastewater treatment: Current developments and future directions

Coffee processing wastewater (CPWW) treatment through conventional techniques is less efficient due to the inherent characteristics of CPWW, low reaction kinetics, and the presence of toxic and/or recalcitrant compounds. Therefore, advanced oxidation processes (AOPs) emerge as a promising avenue for their treatment. These AOPs leverage highly reactive oxidants, such as hydroxyl radicals (center dot OH), to effectively degrade and mineralize a wide spectrum of pollutants present in CPWW. The AOP approaches include ozone-based, electrical energy-based, Fenton-based, and plasma-based processes, and their combinations have often resulted in higher pollutant removal efficiency. In this context, the pollutant removal mechanisms of the aforementioned processes have been critically discussed. Besides, the current developments and future directions for the treatment of CPWW have also been delineated. The treatment of CPWW through the AOP approach might cater to attaining the United Nations Sustainable Development Goals, aimed at creating a healthy planet with accessibility to clean water.