Removing ammonium from aquaculture ponds using suspended biocarrier-immobilized ammonia-oxidizing microorganisms

In this study, polyethylene filter cotton (PFC) was used as a suspended biocarrier to remove ammonium from aquaculture ponds. The concentration of the ammonia-oxidizing bacteria (AOB amoA gene reached ~107 copies cm−3 in the PFC after 16–19 days of incubation, whereas only 101–102 copies cm−3 were present in the aquaculture water. The effects of temperature, pH, and dissolved oxygen (DO) concentration on the nitrification rate were evaluated in the laboratory. The nitrification rate of PFC enriched with AOB reached 0.035 ± 0.002 mg N cm−3 PFC h−1 measured at pH 7.0–8.5, 28 °C, and a DO concentration of 6.0–7.0 mg L−1. These results suggest that the use of PFC as a suspended biocarrier in aquaculture ponds is a feasible and cheap method for removing ammonium ion in situ.