Facual Analysis of Granule Flotation in Brewery Wastewater Treatment Plants by by Fluorescence in situ Hybridization Method

摘要

The factors that change the microbial distribution and consequently the flotation of brewery granules were investigated using laboratory-scale upflow anaerobic sludge blanket (UASB) reactors and the fluorescence in situ hybridization (FISH) method. The startup operations of laboratory-scale UASB reactors fed with acetate-based sythetic wastewater, in which the loading rate was maintained at 0.1g COD/gVSS/d (Run 1) and increased in a stepwise manner from 0.1 gCOD/gVSS/d to 1.0 gCOD/gVSS/d (Run 2), generated methanogen colonies near the granule surface, while the overloading operation at 1.0gCOD/gVSS/d from the startup (Run 3) resulted in the formation of methanogen colonies deep in the granules. In each run, a proportion of the granules floated when overloaded at 2.0gCOD/gVSS/d and circulation was stopped. The ratio of floating granules increased as the methanogen-growing region increased. On the other hand, the Bacteria layer on the granule surface, which is also considered as a possible caused of granule flotation, was not formed by the inflow of other organic acieds such as propionate and lactate. Glucose caused formation of a 5-mum-thick surface Bacteria layer, but the granules were will resistant to flotation. Interfusing of air under glucose feeding caused the formation of a Bacteria layer over 50 mum thick leading to granule flotation.