Abstract
Hydrogen sulfide in a biogas can be removed economically by adding a small amount of air into the headspace of a digester. A microbial mat developed in the headspace of the digester as a result of the sulfide oxidation. Microbial mats containing sulfur filaments developed in the headspace of the digester. Little is known about microbial ecology and the environment in the digester with a biological desulfurization system. This study is an attempt to clarify the internal environment and the microbial ecology in the mats. The result of microelectrode experiments revealed that the O2/S2- supply ratio as a reaction-controlling factor was 0.45 which is a suitable range for sulfur formation. The results of CARD-FISH analysis suggested that Sulfurimonas sp. related bacteria were active sulfur-oxidizing bacteria producing sulfur from H2S and responsible for the formation of filamentous sulfur.
