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

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 CaCl₂ as a clarifier and the optimization of DAF operational parameters using a central composite rotational design. With CaCl₂, removals of 65% turbidity and 70% UV₂₅₄ were achieved, while treatment without the salt reached only 40% turbidity and no significant UV₂₅₄ reduction. The optimal conditions with CaCl₂ were 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 CaCl₂ in enhancing the DAF performance for CPW treatment.