Department of Physical and Biological Sciences, Western New England University, Springfield, MA, United States.
College of Environmental Science and Engineering, Beijing Forestry University, Beijing, China.
Adv Appl Microbiol. 2019;106:113-192. doi: 10.1016/bs.aambs.2018.10.003. Epub 2018 Dec 10.
Many wastewater treatment plants in the world do not remove reactive nitrogen from wastewater prior to release into the environment. Excess reactive nitrogen not only has a negative impact on human health, it also contributes to air and water pollution, and can cause complex ecosystems to collapse. In order to avoid the deleterious effects of excess reactive nitrogen in the environment, tertiary wastewater treatment practices that ensure the removal of reactive nitrogen species need to be implemented. Many wastewater treatment facilities rely on chemicals for tertiary treatment, however, biological nitrogen removal practices are much more environmentally friendly and cost effective. Therefore, interest in biological treatment is increasing. Biological approaches take advantage of specific groups of microorganisms involved in nitrogen cycling to remove reactive nitrogen from reactor systems by converting ammonia to nitrogen gas. Organisms known to be involved in this process include autotrophic ammonia-oxidizing bacteria, heterotrophic ammonia-oxidizing bacteria, ammonia-oxidizing archaea, anaerobic ammonia oxidizing bacteria (anammox), nitrite-oxidizing bacteria, complete ammonia oxidizers, and dissimilatory nitrate reducing microorganisms. For example, in nitrifying-denitrifying reactors, ammonia- and nitrite-oxidizing bacteria convert ammonia to nitrate and then denitrifying microorganisms reduce nitrate to nonreactive dinitrogen gas. Other nitrogen removal systems (anammox reactors) take advantage of anammox bacteria to convert ammonia to nitrogen gas using NO as an oxidant. A number of promising new biological treatment technologies are emerging and it is hoped that as the cost of these practices goes down more wastewater treatment plants will start to include a tertiary treatment step.
世界上许多污水处理厂在将废水排放到环境中之前并未去除废水中的活性氮。过量的活性氮不仅对人类健康有负面影响，还会导致空气和水污染，并可能导致复杂的生态系统崩溃。为了避免环境中过量活性氮的有害影响，需要实施确保去除活性氮的三级废水处理实践。许多污水处理设施依赖于化学物质进行三级处理，但是，生物脱氮实践更具环保性和成本效益。因此，人们对生物处理的兴趣正在增加。生物方法利用参与氮循环的特定微生物群，通过将氨转化为氮气，从反应器系统中去除活性氮。已知参与此过程的生物体包括自养氨氧化细菌、异养氨氧化细菌、氨氧化古菌、厌氧氨氧化菌 (anammox)、亚硝酸盐氧化菌、完全氨氧化菌和异化硝酸盐还原微生物。例如，在硝化-反硝化反应器中，氨和亚硝酸盐氧化菌将氨转化为硝酸盐，然后反硝化微生物将硝酸盐还原为非活性的氮气。其他脱氮系统（anammox 反应器）利用 anammox 细菌利用 NO 作为氧化剂将氨转化为氮气。一些有前途的新型生物处理技术正在涌现，人们希望随着这些实践的成本降低，更多的污水处理厂将开始包括三级处理步骤。
