Abstract:  It is regarded as an environment friendly way to obtain aquatic products by realizing the re-use of aquaculture water and closed production in recirculating aquaculture systems. The biological conversion of nitrite nitrogen to nitrate nitrogen is called Nitrification, which is the most common way to control ammonia-nitrogen in the present recirculating aquaculture systems.  Fixed-film biological filter, as a common way to realize nitrification and a key unit in a recirculating aquaculture system, can provide attachment surfaces for nitrobacteria to form bio-films. It can be divided into several types according to the different ways of contact between the bio-film carrier and the water flow or the different positions where the bio-film carrier flows through the fixed-film biological filter in the water body. The paper reviewed several types of frequently-used fixed-film bio-filters in recirculating aquaculture systems including trickling bio-filter, submerged bio-filter, fluid bed bio-filter, moving bed bio-film reactor,etc. in which the advantages and disadvantages of them were analyzed and compared, and specific cases were taken to illustrate the designs of bio-filters, thus providing reference for the construction of circulating aquaculture systems.

Key words: Recirculating aquaculture system, Bio-filtration, Nitrification, Fixed-film

摘要： 采用循环水养殖系统实现养殖用水的重复利用并进行封闭式生产，被认为是一种环境友好的水产品获取方式。自养硝化过程将氨氮经由亚硝酸盐氮转化成硝酸盐氮，是目前封闭式循环水养殖系统中最普遍的一种氨氮控制途径。固定膜式生物过滤器为硝化细菌提供附着基面，形成生物膜，是常用的自养硝化实现方式，也是循环水养殖系统核心的水处理单元。可根据生物膜载体与水流的接触方式或载体流经滤器的水体中的位置分为几种类型。本文综述了滴滤式、浸没式、流化床、移动床等循环水养殖系统中较常用的几种生物过滤器，分析其优缺点并进行比较，同时结合具体案例进行生物过滤器的设计举例，为循环水养殖系统的构建提供参考。

关键词: 循环水养殖系统, 生物过滤, 自养硝化, 固定膜