Abstract

Ammonium (NH₄⁺) oxidation is crucial for nitrogen (N) removal, contributing to regional and global N cycles, but is regarded as limited to a few biological pathways. A novel pathway for NH₄⁺ oxidation and the N cycle is provided in the microbial anaerobic NH₄⁺ oxidation coupled with Fe(III) (ferric iron) reduction, called ferric ammonium oxidation (Feammox). Over the past few years, Feammox, which results in significant loss of N in natural environments, has been detected widely in both terrestrial and aquatic ecosystems. Researchers have revealed various Feammox pathways, end products of nitrate (NO₃^-), nitrite (NO₂^-), and gaseous nitrogen (N₂), and the interactions within the nitrogen and iron-cycle-related microbial communities, which might offer some novel alternative processes for wastewater treatment. However, there are substantial variations among different studies in terms of the key functional microorganisms. The underlying mechanisms of Feammox, as well as the effect of environmental factors, remain poorly understood. In this review of the emerging process, we detail the end-products and microbes involved in the Feammox process and discuss possible mechanisms and the main influential factors. In particular, we assess the potential applications in wastewater treatment based on previous experimental studies and highlight knowledge gaps and future research opportunities.

摘要

铵 (NH ₄ ⁺ ) 氧化对于氮 (N) 去除至关重要，有助于区域和全球 N 循环，但被认为仅限于少数生物途径。_{NH 4} ⁺氧化和N循环的新途径是在微生物厌氧NH ₄ ⁺氧化以及Fe(III)（三价铁）还原中提供，称为三价铁铵氧化（Feammox）。在过去几年中，导致自然环境中 N 大量损失的 Feammox 已在陆地和水生生态系统中广泛检测到。研究人员揭示了各种 Feammox 途径、硝酸盐 (NO ₃ ^- )、亚硝酸盐 (NO ₂ ^- ) 和气态氮 (N₂），以及与氮和铁循环相关的微生物群落之间的相互作用，这可能为废水处理提供一些新的替代工艺。然而，就关键功能微生物而言，不同研究之间存在很大差异。Feammox 的潜在机制以及环境因素的影响仍然知之甚少。在对新兴工艺的回顾中，我们详细介绍了 Feammox 工艺中涉及的最终产品和微生物，并讨论了可能的机制和主要影响因素。特别是，我们根据之前的实验研究评估了废水处理中的潜在应用，并强调了知识差距和未来的研究机会。