Optimization of Dissolved Air Flotation in the Treatment of Coffee Processing Wastewater Using Calcium Chloride

Abstract

Coffee processing wastewater (CPW) is characterized by a high organic load, low pH, and elevated solids, and its improper disposal can cause severe environmental impacts. Coagulation-flocculation followed by dissolved air flotation (DAF) has proven effective for CPW treatment. This study evaluated CaCl2as a clarifier and the optimization of DAF operational parameters using a central composite rotational design. With CaCl2, removals of 65% turbidity and 70% UV254were achieved, while treatment without the salt reached only 40% turbidity and no significant UV254reduction. The optimal conditions with CaCl2were a 5 bar saturation pressure, an 80% recirculation ratio, and a 30 min flotation time; without salt, similar pressures and recirculation ratios were obtained, but the flotation time increased to 36 min. These findings highlight the role of CaCl2in enhancing the DAF performance for CPW treatment.