Brewery Wastewater Treatment Coupled to Green Hydrogen Production through Microbial Electrolysis Cell

Abstract

Brewery wastewater represents a challenging effluent due to its high organic load and variable composition, but also a valuable substrate for resource recovery within circular economy strategies. In this context, here a three-chamber microbial electrolysis cell (MEC) system was operated in continuous flow using real brewery wastewater without any pretreatment, with a bioanode surrounded by two stainless-steel cathodes. The system was operated at an organic loading rate of 0.5 gCOD/(L·d) and with the anode polarized at +0.2 V vs. SHE. Stable hydrogen production was achieved, with an average hydrogen purity of 65.5 ± 0.7% and a cathodic coulombic efficiency of 50 ± 2%. COD mass balance indicated that most of the removed organic matter (69 ± 1%) was converted into electrical current (around 47%), while methane production was negligible (0.8 ± 0.2%). The energy balance resulted in an overall energy efficiency of 43 ± 2%. The results obtained clearly demonstrate the suitability of brewery wastewater as a promising substrate for direct treatment and valorization through biohydrogen production in MEC systems. Kinetic characterization of the bioanode activity as a function of anodic potential also confirmed a good electrocatalytic performance of the bioanode under the selected working potential.