Environmental and economic feasibility of the treatment of dairy industry wastewater by photo-Fenton and electrocoagulation process: Multicriteria optimization by desirability function

Abstract

The objective of this study was to treat of dairy wastewater by two-step optimized process, which included the photo-Fenton (UV/Fe2+/H2O2) followed by electrocoagulation (EC), aiming to achieve environmental and economic feasibility. An empirical statistical model was defined by Box-Behnken Design (BBD) and linked to the mathematical programming of maximization of the parameters that characterized the organic matter removal. The response surface by BBD and parametric effects of main factors of the treatment were rigorously investigated. Multicriteria optimization approach by desirability function has been used to simultaneously minimize operating cost of EC and maximize COD and TOC removals according to desirable current efficiency and electrode dissolution of the Al electrode. The optimized UV/Fe2+/H2O2 treatment conditions (14,000 mg L−1 H2O2; 198 mg L−1 Fe2+ and initial pH 3.5) led to maximum removal of COD (≈ 60%) and TOC (≈ 73%), with a final pH of about 3 after 180 min of reaction, costing around US $ 40.24 per kg COD removed. The minimum energy consumption during EC was reached when ≈ 107.14 A m−2; ≈ 35 min and initial pH ≤ 6 (around US $ 8.97 per kg COD removed). Thus, the potential of two well-known processes were successfully designed, allowing the combination of both to maximize the removal of organic matter, with energy efficiency and, the minimum operating cost.