Abstract Denitrification is a major biological process contributing to nitrate and nitrite reduction. However, this process remains poorly understood at alkaline pH although such conditions can be encountered in natural (e.g. soda lakes) or industrial environments (e.g. geological waste repositories with cementitious materials). To investigate the nitrate reduction (NR) rate for pH > 9.5 in a cementitious environment, several batch reactors were implemented, with cement leachate or with hardened cement paste (HCP). In the experiments carried out with cement leachate, NR dropped from 0.72 mM/h at pH 9.5 to 0.17 mM/h at pH > 11, while the concentration of nitrite increased. The NR was inhibited at pH close to 12, as was the nitrite reduction at pH above 11. In the reactor containing HCP, the NR rate was 0.75 mM/h at pH close to 10. Calcite precipitated on the HCP surface. Epifluorescence microscopy observations coupled with DNA labelling suggested the presence of microorganisms attached to the HCP surface. This was confirmed by biological growth coupled with NR activity after the transfer of the HCP into a new medium, considered to be sterile. The bacterial community analysis showed that the highly selective culture conditions led to the selection of two species: Halomonas sp. and a species known for its versatile metabolism and ability to form biofilms, i.e. Thauera sp.

中文翻译：

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固体胶凝材料强碱性环境下活性污泥微观结构的硝酸盐和亚硝酸盐还原活性

摘要 反硝化作用是促进硝酸盐和亚硝酸盐还原的主要生物过程。然而，这个过程在碱性 pH 值下仍然知之甚少，尽管在自然环境（例如苏打湖）或工业环境（例如具有胶结材料的地质废物库）中可能会遇到这种条件。为了研究水泥环境中 pH > 9.5 的硝酸盐还原 (NR) 率，实施了几个间歇反应器，使用水泥渗滤液或硬化水泥浆 (HCP)。在用水泥渗滤液进行的实验中，NR 从 pH 9.5 时的 0.72 mM/h 下降到 pH > 11 时的 0.17 mM/h，而亚硝酸盐的浓度增加。NR 在 pH 值接近 12 时被抑制，在 pH 值高于 11 时亚硝酸盐的还原也被抑制。在含有 HCP 的反应器中，NR 速率在 pH 值接近 10 时为 0.75 mM/h。方解石沉淀在 HCP 表面。荧光显微镜观察加上 DNA 标记表明存在附着在 HCP 表面的微生物。在将 HCP 转移到被认为是无菌的新培养基后，生物生长和 NR 活性证实了这一点。细菌群落分析表明，高度选择性的培养条件导致了两个物种的选择：Halomonas sp。以及以其多功能代谢和形成生物膜的能力而闻名的物种，即 Thauera sp。细菌群落分析表明，高度选择性的培养条件导致了两个物种的选择：Halomonas sp。以及以其多功能代谢和形成生物膜的能力而闻名的物种，即 Thauera sp。细菌群落分析表明，高度选择性的培养条件导致了两个物种的选择：Halomonas sp。以及以其多功能代谢和形成生物膜的能力而闻名的物种，即 Thauera sp。