The effects of C/N ratio on the production of volatile fatty acids and the metabolic pathway of anaerobic fermentation of sewage sludge
C/N对污泥厌氧发酵产酸类型及代谢途径的影响

The effects of initial carbon-nitrogen ratio on the metabolic pathway leading to volatile fatty acid (VFA) production were investigated during anaerobic fermentation of sewage sludge. When the initial C/N ratio was 12, the main product was acetic acid, while propionic and acetic acids became the main products at an initial C/N of 56. With the increase of initial C/N to 156, butyric acid became the dominant volatile fatty acid. The shift of the acid fermentation type partly resulted from the change of the dominant bacterial populations in the system. During acetate type fermentation, the acetic acid-producing bacterial genus Peptostreptococcus was dominant. In propionate fermentation, the propionic acid-producing bacteria genus Propionibacterium became dominant. For the butyrate type fermentation, Clostridium dominated the bacterial community in the sludge. With the increase of C/N ratio, the main metabolic pathway resulting in the accumulation of the predominant VFA changed from the Stickland reaction to the pyruvic acid pathway of glycolysis.