Toward a greener dairy industry: Optimization of coagulation–flocculation for sustainable cheese whey treatment

Cheese whey is a high-strength dairy effluent with low biodegradability and significant environmental impact when discharged untreated. This study optimized the coagulation–flocculation treatment of real Minas Frescal cheese whey using an anionic polyacrylamide (APA) coagulant and response surface methodology with a face-centered central composite design. Unlike prior studies focused on synthetic or simplified effluents, this work demonstrates a validated optimization strategy under realistic conditions, integrating multiple removal criteria (BOD₅, turbidity, lactose, soluble solids, and total solids) with sustainability assessment. Statistical modeling revealed that pH was the most influential factor for BOD₅, soluble solids, and total solids removal, while APA dose predominantly affected turbidity and stirring parameters influenced lactose removal. Optimal conditions (pH 4, APA dose 91 mg L−1, 48 rpm, 15 min) achieved removals of 78.7 % BOD₅, 95.7 % turbidity, 36.9 % lactose, 77.6 % soluble solids, and 25.1 % total solids, with deviations below 8.5 % between predicted and experimental results. Greenness assessment (Path2Green score = 0.614) highlighted strengths in pollutant removal efficiency, residue valorization, and applicability to other agro-industrial effluents, while indicating limitations in coagulant sustainability and scalability. By coupling predictive optimization with sustainability metrics, this study provides one of the first validated physicochemical strategies tailored to real high-strength cheese whey, advancing both environmental compliance and methodological rigor.