Water contamination is a growing environmental issue. Several harmful effects on human health and the environment are attributed to nitrogen contamination of water sources. Consequently, many countries have strict regulations on nitrogen compound concentrations in wastewater effluents. Wastewater treatment is carried out using energy- and cost-intensive biological processes, which convert nitrogen compounds into innocuous dinitrogen gas. On the other hand, nitrogen is also an essential nutrient. Artificial fertilizers are produced by fixing dinitrogen gas from the atmosphere, in an energy-intensive chemical process. Ideally, we should be able to spend less energy and chemicals to remove nitrogen from wastewater and instead recover a fraction of it for use in fertilizers and similar applications. In this review, we present an overview of various technologies of biological nitrogen removal including nitrification, denitrification, anaerobic ammonium oxidation (anammox), as well as bioelectrochemical systems and microalgal growth for nitrogen recovery. We highlighted the nitrogen removal efficiency of these systems at different temperatures and operating conditions. The advantages, practical challenges, and potential for nitrogen recovery of different treatment methods are discussed.

水污染是一个日益严重的环境问题。对人类健康和环境的若干有害影响归因于水源的氮污染。因此，许多国家对废水中的氮化合物浓度都有严格的规定。废水处理使用能源和成本密集的生物过程进行，该过程会将氮化合物转化为无害的二氮气。另一方面，氮也是必需的营养素。人造肥料是通过消耗大量能源的化学过程将大气中的二氧化氮固定下来而制成的。理想情况下，我们应该能够花费更少的能源和化学物质从废水中去除氮，而将其中的一部分回收用于肥料和类似应用。在这篇评论中 我们概述了各种生物脱氮技术，包括硝化，反硝化，厌氧铵氧化（anammox）以及生物电化学系统和微藻生长以回收氮。我们着重介绍了这些系统在不同温度和运行条件下的脱氮效率。讨论了不同处理方法的优势，实际挑战和氮回收潜力。