Ferrioxalate-induced solar photo-Fenton system for the treatment of winery wastewaters

In this study, the mineralization of wastewater from an actual winery using a ferrioxalate-induced solar photo-Fenton process was analyzed. Their main characterization parameters were: Total Organic Carbon: 2674 mg L−1; total solids: 12.06 mg L−1; sedimentable solids: 0.80 ml L−1 and pH: 12.40. First, a physico-chemical pre-treatment of the raw wastewater was conducted, using either coagulation–flocculation or precipitation methods. Next, a photochemical reaction was carried out in a pilot plant consisting of a compound parabolic collector (CPC) solar reactor to remove the Total Organic Carbon (TOC) content of the wastewater. An optimization study was performed combining a multivariate experimental design and Neuronal Networks that included the following variables: the initial concentrations of H2O2, Fe(II) and oxalic acid (H2C2O4), temperature and solar power. Under optimal conditions, 61% TOC removal from the treated water was achieved in 360 min. Temperature and the initial concentrations of H2O2 and oxalic acid were the most significant factors affecting the wastewater mineralization. A detailed analysis of the reaction was performed. The correlation between consumed hydrogen peroxide and removed TOC was found to remain constant. Thus the addition of H2O2 can be used to control the degree of mineralization for this type of wastewater. OH radicals were the main oxidative intermediate species in the process, although hydroperoxyl (HO2), singlet oxygen (1O2), triplet oxygen (O23) and the superoxide radical anion (O2−) also played a role. Photocatalytically degraded wastewater, containing significant residual organic content, can be treated at a later stage by a biological process, thus reducing the cost of its total mineralization using just photochemical oxidation methods.

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► We have studied the mineralization of winery wastewaters using solar light with ferrioxalate.
► Under optimal conditions, 61% TOC was achieved in 336 min.
► The addition of H2O2 can be used to control the mineralization degree of this type of wastewaters.
► OH radicals were the main oxidative intermediate species in the process.
► A biological process after photocatalytic treatment could reduce the total cost of treatment.