Abstract

This study evaluated the impact of anodic oxidation (AO) with a boron-doped diamond (BDD) anode, as an electrochemical pretreatment to enhance biohydrogen (bio-H2) production from winery wastewater (WW) during dark fermentation (DF). The integration of AO and DF aimed to couple the enhancement of substrate biodegradability with renewable energy generation through controlled modification of substrate characteristics. Electrochemical experiments were conducted under different current densities (i.e., 20, 30, 40 and 60 mA cm−2), supporting electrolyte concentrations (i.e., 30 and 50 mM NaCl), and electrolysis times (i.e., 0.5 and 1.0 h) to determine their effects on bio-H2 yield. The results demonstrated that BDD pretreatment substantially improved substrate biodegradability and fermentative performance. The highest bio-H2 yield was obtained with 0.5 h of pretreatment, 30 mM NaCl, and 60 mA cm−2, corresponding to 331.23 ± 1.74 N mL H2 g−1 COD, representing a 75% increase compared to WW without pretreatment. However, prolonged electrolysis and higher current or salinity levels caused substrate over-mineralization, resulting in a yield decrease of up to 14%. In the sequential AO-DF configuration with real WW, bio-H2 production reached 52.1 ± 0.3 N mL H2 g−1 COD, 134% higher than the control assay, accompanied by volatile fatty acid formation (i.e., 1833.33 mg L−1). These findings confirm that controlled AO using a BDD anode effectively enhances WW biodegradability and bio-H2 yield. Overall, this hybrid AO-DF system provides a sustainable and technically robust approach for bioenergy recovery.