The olive oil industry generates large amounts of wastewater (OMW) with low biodegradability and high toxicity, namely due to the presence of phenolic compounds. These characteristics reduce the potential of managing it through anaerobic digestion (AD). The objective of this work is to evaluate the possibility of using a heterogeneous Fenton process with iron filings (IF) to improve the properties of OMW and enhance biogas production through AD. Response surface methodology (RSM), based on the Box-Behnken design (BBD), was applied to evaluate the impact of pH conditions (3, 5 and 7), H 2 O 2 dosage (1, 2.5 and 4 g/L), and IF dosage (0.5, 1 and 1.5 g/L) on maximizing biodegradability, total phenolic compounds (TPh) removal and minimizing chemical oxygen demand (COD) degradation. The optimal conditions predicted by the regression model were pH 3, 3.3 g/L of H 2 O 2 , and 0.9 g/L of IF, which increased biodegradability to 0.37 and achieved removal efficiencies of 88% for TPh and 21% COD. The maximum methane yield in AD was 89 NmLCH 4 /gCOD i , representing a 46% increase for the effluent pretreated at pH 7 with 2.5 g/L of H 2 O 2 and 0.5 g/L of IF during the oxidative process. The addition of IF in AD enhanced methane production by 53% and reduced H 2 S formation by 94% at a dosage of 0.5 g IF/L. Thus, the presence of this iron source can be highly relevant to improving methane yield while minimizing H 2 S production. • Olive oil production generates olive mill wastewater (OMW) with high environmental impact. • Heterogeneous Fenton pretreatment improves OMW anaerobic digestion. • Methane production increased by 46% compared to raw OMW. • The addition of iron filings to AD can enhance CH₄ production while simultaneously reducing H₂S levels.
Vaz et al. (Sun,) studied this question.