Hydrogen gas production from vinegar fermentation wastewater by electro-hydrolysis: Effects of initial COD content

Vinegar fermentation wastewater with different initial COD contents (9.66–48.6 g L−1) were used for hydrogen gas production with simultaneous COD removal by electro-hydrolysis. The applied DC voltage was constant at 4 V. The highest cumulative hydrogen production (3197 ml), hydrogen yield (2766 ml H2 g−1 COD), hydrogen formation rate (799 ml d−1), and percent hydrogen (99.5%) in the gas phase were obtained with the highest initial COD of 48.6 g COD L−1. The highest energy efficiency (48%) was obtained with the lowest COD content of 9.66 g L−1. Hydrogen gas production by water electrolysis was less than 250 ml and wastewater control resulted in less than 25 ml H2 in 96 h. The highest (12%) percent COD removal was obtained with the lowest COD content. Hydrogen gas was produced by reaction of (H+) ions present in raw WW ( pH = 3.0) and protons released from acetic acid with electrons provided by electrical current. Electro-hydrolysis of vinegar wastewater was proven to be an effective method of H2 gas production with some COD removal.