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• Nitrite Reduction Efficiency of Bacillus polymyxa Spores in Freshwater, Brackish Water, and Shrimp Pond Water

  Le Viet Dung, Sam Van Hai

  Date Received: 21-03-2025 / Date Accepted: 20-05-2025 / Date Published: 30-05-2025

   Abstract PDF (VIETNAMESE)

  High nitrite concentrations are toxic to aquatic animals. This study evaluated the capability of Bacillus polymyxa spores introduced from India in reducing nitrite levels in controlled environments and shrimp pond water. A dose of 1g spores (5.3 × 10⁹ CFU/g) was added to freshwater, brackish water (17ppt), and shrimp pond water (17ppt) containing nitrite concentrations of 0.5, 2.5, 5.0, 7.5, and 10 mg/l. After 24 hours of aeration in freshwater, nitrite was completely reduced only at initial concentrations of 0.5 and 2.5 mg/l, while higher concentrations showed no significant reduction. In contrast, nitrite levels in brackish water and shrimp pond water decreased to near zero within 16 hours. The highest nitrite reduction rate of 0.6 mg/l/h was observed at an initial concentration of 10 mg/l in both brackish water and shrimp pond water. These findings indicate that B. polymyxa spores are more effective in nitrite removal in brackish water than in freshwater. Further research is needed to assess their practical application in brackish water aquaculture systems.

  DOI: https://doi.org/10.31817/tckhnnvn.2025.23.5.05

• Assessment of Surface Water Quality in Lang Sen Wetland Reserve Tan Hung District, Long An Province in Dry Season

  Le Diem Kieu, Pham Quoc Nguyen

  Date Received: 20-07-2023 / Date Accepted: 19-02-2025 / Date Published: 28-02-2025

   Abstract PDF (VIETNAMESE)

  The study was conducted to assess the current status of surface water quality in Lang Sen Wetland Reserve, Long An Province. Surface water quality of the reserve was surveyed in the dry season at 5, 6, 9, 10, 11 and 12 sub-zone (3 sample points/ sub-zone) using physical and chemical parameters of water. The results showed that the concentrations of total suspended solids, dissolved oxygen, chemical oxygen, total nitrogenof water in the sub-zones ranging 16.8-30.9; 0.67-1.73; 15.5-44.3; 0.99-3.34 mg/l, respectively, not meeting the standard justified in QCVN 08:2023/BTNMT. In addition, the electrical conductivity, total dissolved solids, turbidity, and nitrite nitrogen were also high that may affect aquatic organisms. Therefore, it is necessary to take measures to effectively monitor and manage water quality, especially in sub-zones 9 and 10 to ensure a favorable water environment for the conservation of large fish species in the reserve.

  DOI: https://doi.org/10.31817/tckhnnvn.2025.23.2.09

• Bacillus sp. Isolated from Goose Grass (Eleusine indica) Enhances the Removal Efficiency of Ammonium in Shrimp Aquaculture

  Do Quang Trung, Tran Thi Tuyet Thu, Luu The Anh

  Date Received: 03-08-2021 / Date Accepted: 21-01-2022

   Abstract PDF (VIETNAMESE)

  Treatment of aquaculture wastewater by biological method is being more attractive to the scientists. This study aimed to screen the salt-tolerant and ammonia-oxidizing Bacillusendophytic bacteria having potential to reduce ammonium levels in shrimp aquaculture wastewater. In this study, eight Bacillusstrains were screened from endophytic bacteria isolated from gooose grass. Among these strains, two strains, MT50 and MT51 showed the highest efficiency for ammonium removal (80.36 and 82.24%, respectively). They optimally grew at pH of 7 and in highly salty condition (4% NaCl). Investigation in laboratory conditions for their ability in improving shrimp aquaculture wastewater showed that both Bacillusstrains had ammonium removal from 72.25 and 78.85% at day 7th. Notably, strain MT50 in combination with unsterilized shrimp-wastewater presented the highest ammonium removal efficiency (79.91%) with 1% cell suspension at day 4th. The results also showed the nitrite and nitrate production in all experiments and these compounds were removed by the selected Bacillusspecies. Results suggested that tưo Bacillussp. isolated might be used as heterotrophic nitrification-aerobic denitrification species.