Dissolved air flotation optimization for treatment of dairy effluents with organic coagulants

The objective of this work was to optimize the conditions of dairy effluent treatment by dissolved air flotation (DAF) at the chemically assisted primary treatment level using the combined polyacrylamide (PAM) and Tanfloc coagulants. For this, the effect of coagulant dosing and pH on the effluent turbidity removal was studied using a central composite rotatable design (CCRD). Synthetic wastewater was used in the optimization phase, and after optimization, the system was used to treat real dairy wastewater in order to determine the pollutant removal efficiency. Coagulation and flocculation tests were performed in jar test equipment and flotation in a flotastest, whose operating conditions were optimized. The results were excellent with respect to turbidity, obtaining removal efficiency above 90 % for most treatments. The regression model obtained was quadratic and significant at 5 % probability, whose R² was 97.41 %. The model has been validated and can be used for predictive purposes. The optimum point for turbidity removal was with 758.3 mg L−1 of PAM combined with 205.4 mg L−1 of Tanfloc at pH 7.6. Expressive reductions in solids, organic matter, nutrients, oils, and greases were achieved when the system was employed for treatment of real dairy wastewater.