Anaerobic co-digestion of sewage sludge and food waste for hydrogen and VFA production with microbial community analysis

Abstract

In this study, the anaerobic co-digestion of food waste (FW) and sewage sludge (SS) was investigated for the production of hydrogen and volatile fatty acids (VFAs). The results showed that the anaerobic co-digestion of these materials enhanced the hydrogen content by 62.4% (v/v), 29.89% higher than that obtained by FW digestion alone, and the total VFA production reached at 281.84 mg/g volatile solid (VS), a 8.38% increase. This enhancement was primarily resulted from improvements in the multi-substrate characteristics, which were obtained by supplying a higher soluble chemical oxygen demand (23.78–32.14 g/L) and suitable a pH (6.12–6.51), decreasing total ammonia nitrogen by 18.67% and ensuring a proper carbon/nitrogen ratio (15.01–23.01). Furthermore, maximal hydrogen (62.39 mL/g VS) and total VFA production potential (294.63 mg/g VS) were estimated using response surface methodology optimization, which yielded FW percentages of 85.17% and 79.87%, respectively. Based on a pyrosequencing analysis, the dominant bacteria associated with VFA and hydrogen production were promoted under optimized condition, including members of genera Veillonella and Clostridium and the orders Bacteroidales and Lactobacillales.