Modeling and optimization of coagulation-flocculation process to remove high phosphate concentration in wastewater from a metal-mechanic industry

In this work, the performance of a coagulation-flocculation plant to treat wastewater from a metal-mechanic industry located in an industrial park of Queretaro city, Mexico is studied. Wastewater samples were obtained from the homogenization tank and treated with the employed industrial reactants through an experimental jar test to obtain statistical data. Then, a response surface methodology with ANOVA analysis was used to model the process, and the ε-constraints methodology was used to optimize the coagulation-flocculation process in terms of economic and environmental impact. Optimal operating conditions were found at 400 mg L − 1 of calcium hydroxide dose, 0.723 mL L − 1 of aluminum salts dose, 3.32x10 − 3 mg L − 1 flocculant dose and 100 rpm of agitation speed. The results showed an improvement of phosphates removal, but a minimal increment of 1.01% of operational costs regarding to the current operating conditions.