Total ammonia nitrogen (TAN) concentration is often a key limiting water quality parameter in intensive aquaculture systems. Removing ammonia through biological filtration is thus the first objective in recirculating aquaculture system design. In this study, the performance characteristics of a steady-state nitrification biofilm were explored using a series of reactors. Four nitrification kinetics parameters were estimated using the data collected from the experimental system, including minimum TAN concentration, half saturation constant, maximum TAN removal rate and maximumspecific bacterial growth rate. Experimental daa showed that a minimum TAN concentration was needed to support a steady-state nitrification biofilm. For the temperature of 27.2 degree, the mean minimum TAN concentration was 0.07 mg/l. For a single substrate-limiting facotr, the relationshipo between TAN removal rate (R) and TAN concentration (S) was represented by an empirical equation [R=1859(S-0.07)/S(+1.93)]. The characteristics of nitrite oxidation were also demonstrated by the experiment system. The results of this study will help to better understand the characteristics of nitrification biofilters applied in recirculating auqaculture systems.
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