Influence of filter medium type, temperature and ammonia production on nitrifying trickling filters performance

This work focuses on the achieving of optimal design and modelling of nitrifying trickling filters for closed circuit aquaculture turbot (Psetta maxima) farms. Several process parameters influential in nitrifying filtration were established on experimental biofilters and their efficiency was tested, based on the removal of nitrogen contained in total ammonia nitrogen (N-TAN) in a fixed time (24 h). Those process parameters were filter media types (Type A Biofill®, BactoBalls® and MECHpro® rings), temperatures (24.3 °C, 19.0 °C, 15.3 °C) and production of TAN (1.5, 3.0 and 4.5 g per day) while other process parameters values remained constant. TAN production was simulated with the addition of ammonium chloride (NH4Cl) in the recirculation system. Constant measuring of the total ammonia nitrogen concentration in the biofilter effluent was required to perform a model of N-TAN fluctuation based on a specific feeding regime and to ascertain performance differences between biofilters.At the end of the experiment, notable differences were observed in the ammonia removal rates depending on different process parameters. The BactoBalls® filter medium led to the highest mean N-TAN removal rates (0.24 g N-TAN removed m−2 day−1). The N-TAN removal rate generally increased with higher temperatures, the trials with the highest mean temperature (24.3 °C) led to the highest mean N-TAN removal rate (0.26 g N-TAN removed m−2 day−1). Similarly, the N-TAN removal rate increased with high TAN production. The trials in which production was 4.5 g per day showed the highest N-TAN mean removal rate (0.27 g N-TAN removed m−2 day−1).

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