Enhanced removal of phenol from biorefinery wastewater treatment using enzymatic and Fenton process

The valorisation of biomass has been commonly carried out in biorefineries. The environmental concerns about these processes have not been intensely considered, demanding further investigations. Particularly, phenols are founded in high concentrations in biorefinery wastewater and are considered compounds of major concern. In this study, we evaluated the bioconversion of phenols by enzymatic treatment using the enzyme Horseradish peroxidase (HRP) and the Fenton process. The results showed an enzymatic phenol conversion of 97.5% at pH 7.0, enzyme activity of 0.8 U/mL and hydrogen peroxide concentration of 1.61 g/L. So as to enhance the treatment, we evaluate the Fenton reaction as a complementary process for further remaining phenol conversion. The best conditions for Fenton process were achieved using a hydrogen peroxide concentration and [H₂O₂]:[Fe] ratio of 3.90 g/L and 74, respectively, and the obtained phenol concentration in the treated wastewater was 0.11 mg/L. Chromatography analysis showed that 2-methoxyphenol was the majority compound in the original wastewater, which was subsequently precipitated by the enzymatic treatment. Furthermore, many physicochemical parameters were modified due to the treatment, such as biochemical oxygen demand, chemical oxygen demand and total organic carbon, with removal efficiencies of around 97, 49 and 46%, respectively. HRP combined with Fenton can be considered as an alternative methodology for the biorefinery wastewater treatment, especially regarding the phenols conversion.