State Key Laboratory of Pollution Control and Resources Reuse, School of Environmental Science and Engineering, Tongji University, 1239 Siping Road, Shanghai 200092, China.
Shanghai Key Laboratory of Atmospheric Particle Pollution and Prevention (LAP3), Department of Environmental Science and Engineering, Fudan University, Shanghai 200438, China.
Environ Sci Technol. 2022 Jul 19;56(14):10317-10328. doi: 10.1021/acs.est.2c01914. Epub 2022 Jun 27.
Given hydroxylamine accumulation in various nitrification systems and its potential mechanism in regulating the subsequent denitrification process were unraveled in this study. Hydroxylamine (>0.5 mgN/L) immediately induced nitrite accumulation of activated sludge by inhibiting the activities of nitrite reductases and their electron transport modules (Complex III and cytochrome c). Moreover, long-term exposure to 0.5-2.5 mgN/L hydroxylamine accelerated the functional transformation from denitrification to denitratation under low C/N conditions. However, genome-centric metagenomics indicated that a genotypic complete rather than truncated denitrifier TJ127 was enriched and mainly responsible for acetate storage and nitrate reduction of the denitratation community. Interestingly, its enrichment resulted in nitrite production and reduction sequentially but reduced nitrate only to nitrite under carbon-limited conditions (C/N ≤ 3.0). Thus, it showed higher tolerance to hydroxylamine than the concurrent phenotype denitrifiers in activated sludge. Moreover, due to its higher anoxic storage capability in the feast phase, this enrichment became highly specialized by decreasing the feast/famine ratio, and thus a satisfactory denitratation performance was still maintained without hydroxylamine. These results suggested that the transient release of hydroxylamine from nitrification may interfere with subsequent denitrification metabolism, but its continuous accumulation is beneficial for achieving denitratation, which could steadily provide nitrite for mainstream anammox.
本研究揭示了在各种硝化系统中羟胺的积累及其潜在的调节后续反硝化过程的机制。羟胺（>0.5mgN/L）通过抑制亚硝酸盐还原酶及其电子传递模块（复合物 III 和细胞色素 c）的活性，立即引起活性污泥中亚硝酸盐的积累。此外，长期暴露于 0.5-2.5mgN/L 的羟胺在低 C/N 条件下加速了从反硝化到异化反硝化的功能转化。然而，基于基因组的宏基因组学表明，一种基因型完整而非截短的反硝化菌 TJ127 被富集，并主要负责异化反硝化群落中乙酸盐的储存和硝酸盐的还原。有趣的是，其富集导致亚硝酸盐的产生和还原依次进行，但在碳限制条件下（C/N ≤ 3.0）仅将硝酸盐还原为亚硝酸盐。因此，它对羟胺的耐受性高于活性污泥中同时存在的表型反硝化菌。此外，由于其在饱食期具有更高的缺氧储存能力，这种富集通过降低饱食/饥饿比变得高度专业化，因此在没有羟胺的情况下仍能保持令人满意的异化反硝化性能。这些结果表明，硝化过程中羟胺的短暂释放可能会干扰随后的反硝化代谢，但羟胺的持续积累有利于实现异化反硝化，从而稳定地为主流厌氧氨氧化提供亚硝酸盐。
