Ammonia and nitrite nitrogen removal in shrimp culture by Vibrio alginolyticus VZ5 immobilized in SA beads

Abstract

The toxicity of nitrogen in the shrimp culture water has been well established. In this study, SA beads composed of Vibrio alginolyticus VZ5, sodium alginate (SA) and sugarcane bagasse were used for ammonia nitrogen (NH₄-N) and nitrite nitrogen (NO₂-N) removal. A 50-day cultivation experiment was carried out in aquaria to evaluate the activity of the SA beads in shrimp culture. The results indicate that SA beads have a maximum capacity of 1.06 × 10⁸ colony-forming units (cfu)/bead. However, the optimal initial density of the bacteria embedded in the SA beads is 10⁴–10⁵ cfu/bead. The maximum NO₂-N degradation rate achieved for the SA beads was 8.44 mg/L/day, and the average NO₂-N degradation per bead was 0.06 mg. The addition of a carbon source accelerated the degradation of NH₄-N and NO₂-N by the SA beads. The NH₄-N and NO₂-N concentrations after treatment with SA beads were below 1.55 and 1.62 mg/L, respectively, at later time points, and these concentrations were significantly lower than in the group without any treatment (P < 0.05, df = 17). There were no significant differences in the NH₄-N and NO₂-N concentrations following treatments with SA beads and water exchange (P > 0.05, df = 29), and the yield resulting from water treatment with SA beads reached approximately 70 % of the yield with water exchange treatment. Moreover, the particulate organic carbon and dissolved organic carbon concentrations in the water were enhanced by the addition of SA beads. At later time points, some of the SA beads had broken down, and the sugarcane bagasse from the SA beads may have served as a carbon source for forming bioflocs. The new approach proved effective for NH₄-N and NO₂-N removal in shrimp culture.