Acetate production by a coupled syntrophic acetogenesis with homoacetogenesis process: Effect of sludge inoculum concentration

Abstract

The effect of sludge inoculum concentration on acetate (Ac) production by a novel coupled system was investigated. The coupled system consisted of a syntrophic acetogenesis phase and a homoacetogenesis phase. The results showed that the inoculum concentration not only affected the acetate production at the syntrophic acetogenesis phase but also that produced at the homoacetogenesis phase. When the inoculum concentration in the syntrophic acetogenesis phase was 4 g l⁻¹, the acetate yield of the coupled system was found to be about 0.36 g Ac g⁻¹ glucose. In addition, when the inoculum concentration in the homoacetogenesis phase was 4 g l⁻¹, a maximum acetate production of 11.2 g l⁻¹ was obtained in the syntrophic acetogenesis phase and the yield of acetate was 0.39 g Ac g⁻¹ glucose. Analysis shows that the variation in acetate yield might be attributed to different metabolic pathways and the imbalance between hydrogen production and hydrogen consumption in the coupled system with different inoculum concentrations.

Keywords:

• anaerobic digestion
• coupled system
• volatile fatty acids
• high strength organic wastewater
• mixed fermentation

Acknowledgements

The authors are grateful for the financial support of the National Natural Science Foundation of China (NSFC Grant No. 50508014) and the National High Technology Research and Development Program (“863” Program) of China (2006AA06Z315).