Removal of ammonium-N from marine recirculating aquaculture by immobilized nitrifiers

Marine nitrobacters were enrichmented, acclimated and used to denitrificate of marine recirculating aquaculture by immobilization in an aquarium of 60 L. After 46 d, the ammonia oxidation rate and the nitrite oxidation rate were both over 8 mg/(L·d) by adjusting the ammonium concentration in appropriate condition. An adsorption experiment was carried out for 15 d with two kinds of PVA beads and the activated carbon beads filled in three plastic columns respectively. And experiments to evaluate the efficiency nitrification of three fixed packed bed column were conducted. Results show that with a hydraulic retention (HRT) of 1 h and the influent ammonia concentration less than 0.6 mg/L, all the three reactors can achieve the efficiency of 100%. When HRT is set in the range of 10-90 min, the highest ammonia-N removal rates of 70 g/(m³·d), 58 g/(m³·d), and 48 g/(m³·d) are figured out for the activated carbon, the PVA beads (2 mm) and the PVA beads (4 mm) reactors respectively with the optimal HRT of 15 min, 18 min, and 22 min.