報告書番号

U99017

タイトル（和文）

排水中の窒素除去に関する研究 5. --活性汚泥中のアンモニア酸化菌の検出とバイオリアクターへの利用--

タイトル（英文）

Development of biological wastewater treatment system for nitrogen removal 5. Detection of ammonia-oxidizing bacteria in an activated sludge and utilization for bioreactor

概要 （図表や脚注は「報告書全文」に掲載しております）

多くのアンモニア酸化菌に共通の遺伝子に結合する蛍光DNAプローブを用いることにより、活性汚泥中のアンモニア酸化菌の簡易な検出が可能となった。活性汚泥中には多量のアンモニア酸化菌が存在することが確認され、そのほとんどが凝塊（フロック）中に存在していることが示された。活性汚泥を固定化して作製したチューブ状ゲルの活性は、純粋培養菌を固定化したゲルより活性は低いものの、馴養することによって比活性で約40%にまで向上した。このチューブ状ゲルの活性の差は、ゲル内部のアンモニア酸化菌の分布が原因のひとつとして考えられた。したがって、アンモニア酸化菌を多量に含む活性汚泥は、純粋培養菌の代わりに窒素除去用バイオリアクターに利用可能であるが、純粋培養菌を固定化したバイオリアクターと同等の活性を有するためには、フロック中に凝集したアンモニア酸化菌の分散等の検討が必要であると思われた。

概要 （英文）

Bioreactor for nitrogen removal requires a large number of ammonia-oxidizing bacteria as a biocatalyst. An activated sludge from wastewater treatment plant is expected to contain many species of ammonia-oxidizing bacteria. It is possible that the activated sludge containing a large number of ammonia-oxidizing bacteria is applied to the bioreactor. In this report, we examined to detect the ammonia-oxidizing bacteria in the activated sludge and use it as a biocatalyst to the bioreactor. In order to detect ammonia-oxidizing bacteria in the activated sludge, the fluorescent oligonucleotide hybridization probe was used to label ammonia-oxidizing bacteria. The probe, complementary to short sequence element within the 16S rRNA of representatives of the lithoautotrophic ammonia-oxidizing bacteria, were labeled with XRITC (X-rhodamine isothiocyanate) and hybridized to fixed cells. By in situ hybridization with the probe, densely packed bacterial aggregates were stained in the activated sludge sample. From the comparison of the ammonia-oxidizing activities of the activated sludge and the pure culture of Nitrosomonas europaea, it was estimated that the concentration of ammonia-oxidizing bacteria in the activated sludge was equal to approximately 107 cells/ml of N. europaea. The artificial wastewater containing 200 mg-N/l of ammonia was aerobically treated by the tubular gel bioreactor containing the activated sludge or pure culture as a biocatalyst. Ammonia in the wastewater was removed by the tubular gel containing the activated sludge, and its nitrification rate increased from 0.64 g-N/day/m2 to 1.8 g-N/day/m2 by acclimatizing to the wastewater. However, its specific activity was approximately 0.4 for the tubular gel immobilized with the pure cultured cells. Bacterial distributions in the acclimatized tubes were examined by the oligonucleotide probe labeling technique. In the tube immobilized with the pure cultured cells, colonies of ammonia-oxidizing bacteria were distributed in the region close to surface of the tube. In contrast, aggregates of ammonia-oxidizing bacteria were sparsely distributed in the tube immobilized with the activated sludge. The nitrification rate of the tubular gels would be affected by the distribution of ammonia-oxidizing bacteria in the gels. Consequently, the activated sludge contained a large number of ammonia-oxidizing bacteria. It was possible to be applied instead of the pure culture cells as a biocatalyst to the bioreactor. Scattering the aggregates of ammonia-oxidizing bacteria in the activated sludge before the immobilization would enable to increase ammonia-oxidizing activity of the bioreactor.

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