Sustainable Treatments for Wastewater Deriving from the Coffee Processing

A large quantity of water is used in the production process of the coffee industry, with a specific production of wastewater up to 20 L/kg of coffee berries. Considering that the current world production of berries is around 10 million metric tons, a huge volume of wastewater is generated, characterized by suspended solids, and high concentration of soluble organic matter, Biological Oxygen Demand (BOD), and Chemical Oxygen Demand (COD). It is a great threat to the soil, surface, and groundwater environment if this wastewater is discharged without treatment. Hence, the treatment of coffee processing wastewater (CPWW) is essential through innovative, sustainable, and eco-friendly techniques. Although conventional biological treatment methods proved to be very efficient, economic constraints and challenges to operational strategies are the limitations. Recently, studies started to test Advanced Oxidation Processes to treat CPWW. Among them, Fenton and solar photo-Fenton process already demonstrated good efficacy to remove recalcitrant molecules. The current presentation reports the findings achieved when these two processes are applied to treat CPWW for COD and color removal. The two sets of runs were carried out with the same operative conditions. The results evidenced similar performances for COD and color removal, except in one case where a better removal was achieved with the solar photo-Fenton process. This pushes further tests to clarify some features and optimize the operative conditions since the solar-driven processes can be efficiently exploited in the countries where the solar irradiance is high, exactly where the coffee berries processing is usually carried out. In this way, the sustainability of wastewater treatment will be enhanced using sunlight.