Effects of C/N ratio on nitrogen removal with denitrification phase after a nitrification-based biofloc aquaculture cycle |
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| Institution: | 1. Shanghai Engineering Research Center of Aquaculture (Shanghai Science and Technology Committee), Shanghai Ocean University, Shanghai 201306, China;2. Key Laboratory of Freshwater Aquatic Genetic Resources (Ministry of Agriculture of PRC), Shanghai Ocean University, Shanghai 201306, China;3. National Demonstration Center for Experimental Fisheries Science Education (Ministry of Education of PRC), Shanghai Ocean University, Shanghai 201306, China;1. Shanghai Engineering Research Center of Aquaculture, (Shanghai Ocean University), Shanghai Science and Technology Committee, Shanghai 201306, China;2. Key Laboratory of Freshwater Aquatic Genetic Resources, (Shanghai Ocean University), Ministry of Agriculture of PRC, Shanghai 201306, China;3. National Demonstration Center for Experimental Fisheries Science Education, (Shanghai Ocean University), Ministry of Education of PRC, Shanghai 201306, China;1. College of Fisheries and Life Sciences of Shanghai Ocean University, Shanghai 201306, China;2. Research and Development Center of Aquacultural Engineering of Shanghai, Shanghai 201306, China;3. Shanghai Collaborative Innovation Center for Aquatic Animal Genetics and Breeding, Shanghai 201306, China |
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| Abstract: | In the current study, we set up a denitrification process to remove the nitrogen pollutants, especially nitrate (NO3–-N), from the wastewater after a nitrification-based biofloc technology (BFT) aquaculture cycle. Five different treatments (CN0, CN1, CN2, CN4 and CN6, respectively) were used, which involved addition of extra carbohydrate with variable ratios of elementary organic carbon to NO3–-N by weight (C/NO3–-N ratio equal to 0, 1, 2, 4, and 6, respectively). With CN2, CN4, and CN6 treatments, NO3–-N was decreased (with increasing alkalinity) to ≤ 6.42 ± 0.30 mg·L?1 and low amounts (close to zero) of nitrite (NO2–-N) were achieved. However, there were high concentrations of residual NO3–-N and/or NO2–-N in CN0 and CN1. CN2 achieved the best denitrification, wherein 81.00 ± 0.95% of the initial input nitrogen was removed. By fitting the equations, the highest nitrogen recycling rate (23.08 mg-N·g-C?1) was achieved with a C/NO3–-N ratio of 4.16. Denitrifying bacteria were the dominant bacteria in all extra carbohydrate added treatment groups. Although denitrifying polyphosphate accumulating organisms contributed to the removal of phosphorus, high concentrations of residual soluble reactive phosphate (SRP) were observed in all treatment groups. Overall, extra addition of carbohydrate with C/NO3–-N ratio ≥ 2 is advisable for nitrogen removal, while the highest nitrogen recycling rate will be achieved with a ratio of 4.16. |
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| Keywords: | Biofloc technology Nitrogen removal Nitrogen recycling Bacterial community |
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