Dosing effect of nano zero valent iron (NZVI) on the dark hydrogen fermentation performance via lake algae and food waste co-digestion

Abstract

The effect of nano zero valent iron (NZVI) on hydrogen production by the co-digestion of dry lake algae and food waste was investigated. The results showed that 10 mg.gTS−1 addition of NZVI improved the performance of the co-digestion system, with the cumulative hydrogen increased by 29.20% to 40.04 mL.gVS−1, compared to that of the control. However, the cumulative hydrogen yield decreased to 14.77 and 5.37 mL.gVS−1 when the NZVI dosage was increased to 20 and 40 mg.gTS−1, respectively. The oxidation reduction potential (ORP) of the reaction system was decreased dramatically to -331∼-490 mV at the initial reaction stage. The degradation rates of carbohydrate and protein also reached their peaks at the NZVI dosage of 10 mg.gTS−1. The concentration of end product in the liquid phase and the dehydrogenase activity was first increased then decreased when enhancing the NZVI dosage. Analysis of the transmission electron microscopy images revealed that excessive NZVI dosage could destroy the cells of microorganisms.