2023 Volume 46 Issue 5 Pages 141-148
Scum floated by biogas generated in Hirano River sediment has caused difficulties because of the combined sewer overflow. The Osaka Prefectural Government conducted a demonstration project for sediment remediation in 2021–2022 by dosing tablets of calcium nitrate. This study used prokaryotic 16S rRNA gene next-generation sequencing to verify the project performance on the basis of changes in the sediment microflora. Sediment at a test site at a depth of 4 m near the Minamibenten Bridge was dosed with chemical tablets every two months. Methanogenic archaea were found to be dominant, but sulfate-reducing bacteria were minor in the anaerobic sediment. The chloroplast DNA sequences of Streptophyta growing in the river surface and settling in the sediment were also detected in some sediment samples. Although methanogenic archaea continued to be dominant, canonical correlation analysis indicated that the microflora at the test site was characterized by their increased proportions of bacteria belonging to Betaproteobacteria, Methylophilales, and Thiobacillus, and by their increased oxidation-reduction potential and decreased total sulfide content.
