抄録
Effects of sulfate concentration and COD/S ratio on the methane production and sulfate reduction in the anaerobic degradation of butyric acid were investigated by using an anaerobic chemostat-type reactor at 35°C. The sulfate concentration and COD/S ratio were changed in the ranges of 68 to 1667 mg·l-1 and 1.5 to 148, respectively. In order to study the competition between the methane producing bacteria (MPB) and sulfate-reducing bacteria (SRB), the COD mass balance, electron flow, sulfur balance and trophic-groups bacterial populations under the different conditions were analyzed quantitatively.
The competition between MPB and SRB was evidently influenced by COD/S ratio. When COD/S ratio was 6.0 or more, the methane production was the main reaction. On the other hand, 67% of the total electron flow was utilized by SRB when COD/S ratio was 1.5. The path way of butyrate degradation and the microflora in the reactor were also affected by COD/S ratio. The numbers of acetate-consuming and H2-consuming MPB decreased from 106 to 104 MPN·ml-1 and 106 to 101 MPN·ml-1, respectively, as COD/S ratio decreased from 148 to 1.5. In the reactor in which a small amount of sulfate was added to the substrate, the numbers of butyrate-consuming and acetate-consuming SRB were enumerated as high as 107 to 108 MPN·ml-1. It is suggested that in sulfate-depleted environment, the butyrate-consuming SRB play an important role in producing H2 and acetate from butyrate, as well as the acetogenic bacteria.
