One of the major challenges in any sustainable aquaculture production systems is the accumulation of nitrogenous waste such as ammonia and its biological nitrification products viz nitrite and nitrate. Considering the bio-security issues, amelioration of these wastes without water exchange can be accomplished only by way of establishing in situ nitrification and denitrification through biofilters/bioreactors activated with nitrifying/denitrifying bioaugmentors. In such systems, coexistence of aerobic denitrifiers, anaerobic ammonia oxidizers (Anammox) and complete ammonia oxidizers (Comammox) together with the autotrophic nitrifiers enhance the coupled nitrification–denitrification. This promotes total nitrogen removal without external carbon supplements or additional anerobic compartment in the system. Various recirculating aquaculture systems (RAS) comprise diverse nitrifying community in biofilters/bioreactors thereby imparting distinctive nitrogen conversion in the system. Meanwhile, the structure and population dynamics of the nitrifying/denitrifying consortia are influenced by the environmental factors forming the decisive factors of the success of the processes. Accordingly, understanding the complexity of nitrifying/denitrifying community composition turns out to be a requirement to facilitate its improvised performance. In this context, the review addresses different biological nitrogen removal systems, significance of nitrification–denitrification in RAS, genetic diversity of the key players in RAS, methods of analysis of their community structure, current application and prospects of the processes in RAS.

中文翻译：

---

循环水产养殖系统中的硝化和反硝化：过程和参与者

一个在任何可持续水产养殖生产体系面临的主要挑战是含氮废物堆积如氨气和其生物硝化产品VI ž亚硝酸盐和硝酸盐。考虑到生物安全问题，这些废物的改善只能通过原位建立的方式来完成，而无需换水。通过用硝化/反硝化生物增强剂激活的生物过滤器/生物反应器进行硝化和反硝化。在这样的系统中，好氧反硝化器、厌氧氨氧化器（Anammox）和完全氨氧化器（Comammox）与自养硝化器的共存增强了硝化-反硝化耦合。这促进了总氮去除，而无需外部碳补充剂或系统中的额外厌氧隔室。各种循环水产养殖系统 (RAS) 在生物过滤器/生物反应器中包含不同的硝化群落，从而在系统中实现独特的氮转化。同时，硝化/反硝化聚生体的结构和种群动态受到形成过程成功的决定性因素的环境因素的影响。因此，了解硝化/反硝化群落组成的复杂性是促进其即兴发挥的必要条件。在此背景下，该综述讨论了不同的生物脱氮系统、RAS 中硝化-反硝化的意义、RAS 关键参与者的遗传多样性、其群落结构的分析方法、RAS 过程的当前应用和前景。