Solar photodegradation of synthetic apple juice wastewater: Process optimization and operational cost study

The mineralization of a synthetic wastewater containing apple juice using a homogeneous solar photo-Fenton oxidation process assisted with ferrioxalate was evaluated as an alternative to or a rapid pretreatment step for conventional anaerobic digestion and can also be used if the water to be treated contains a recalcitrant pollutant. Experimental kinetic constants were fitted using neural networks (NNs) with an 86% confidence level. The effect of the different variables was explained on the basis of the kinetic mechanism. At the selected operating conditions ([H2O2]=6000 ppm, [Fe(II)]=40 ppm, pH=2.7 and [(COOH)2]=40 ppm), 97% mineralization was achieved in 67 min when treating a synthetic wastewater with 700 ppm of total organic carbon (TOC). In total, 6.5 mol of H2O2 were consumed per each mole of total organic carbon removed from solution. The contributions of molecular, radical and photolytic pathways were also studied. The operational costs due to the consumption of electrical energy, reagents and catalysts were calculated. The results showed that the solar photo-Fenton system was economically feasible, able to achieve up to 97% mineralization with a total cost of 1.6 cents €/g TOC removed (10.9 €/m3 of treated water) at a pilot plant scale.

Graphical.abstractFigure optionsDownload as PowerPoint slideHighlights
► This solar process is an environmental alternative for wastewater mineralization.
► Under the selected operation conditions 97% of TOCs were removed in 67 min.
► 6.5 mol of H2O2 were consumed per mol of TOCs removed.
► The radical pathway is the main responsible for the mineralization process.
► The cost for high TOC removals is∼1.6 cent €/g TOC (∼10.9 €/m3).