Study On The Goethite Promoted Anaerobic Digestion Of Algal Biomass

Cyanobacterial blooms are becoming more and more serious and regular as a result of Lake Eutrophication over the last few decades in China. How to achieve the recycling use of cyanobacteria after refloatation becoming one of research topics. Anaerobic fermentation is one of the effective ways of cyanobacteria reclamation. However, the reported methane yield was much lower than the theoretical value and low transformation rate limited the application of anaerobic fermentation. In the current study goethite, which was abundant in the nature, was explored as external additive to improve the methanogenic efficiency in the reactors and the operation parameters were adjusted to optimize the microbial community structure in the anaerobic fermentation process. The mechanisms of the release goethite promoted anaerobic digestion of algal biomass were preliminarily discussed.1) To explore the effects of the methane production and microbial community structure of graphite, anaerobic fermentation reactors of cyanobacteria have been constructed. Results showed that goethite was an effective additive to improve methane production. Goethite addition promoted the degradation rates of proteins and carbohydrate, methane production and productivity. The community analysis results showed that the addition of goethite changed the microbial community structure in the anaerobic reactor and improve the growth of Firmicutes and Methanosaeta.2) Effects of goethite on methane yield, methane production rate, substrate degradation rate and degradation efficiency under different pH were investigated using glucose as the sole carbon source. The results indicated that methane production was increased with the addition of goethite under the different pH values, especially pH 7.5. Community analysis showed that Methanosaeta was the dominant bacterium at different pH values. Bacterial community changes significantly at different pH values and most of the bacteria were acidogenic types. The bacterial diversity index in goethite-added reactors was higher than that in control reactor and the stability of community structure could be benefit to the methane production.3) In order to explain the effects of goethite in acidogenic process, Methanogens inhibitor was dosed in the reactors. The results showed that goethite increased the production of hydrogen and reduced the concentration of propionic acid in liquid phase. Butyric acid-type fermentation was dominant in the process. Goethite promoted the growth of Firmicutes in anaerobic reactors and the dominant bacteria of Firmicutes were Clostridium, Exiguobacterium and Syntrophomonas, which could product acid and oxidize fatty acids, increased the conversion efficiency of the acidogenic and methanogenic phases.