To control the inorganic nitrogen and biofloc concentrations in the biofloc system, it is necessary to intensify the nitrogen removal by nitrification and denitrification. In this study, nitrifiers and aerobic denitrifying bacteria were inoculated into aquaculture wastewater, with 16.80 mg/L of nitrogen input per day after start-up, and by addition of glucose and citrate C/N to 9 and 12, without adding carbon source as control (C/N 6.17). The concentrations of inorganic nitrogen, total nitrogen and biofloc, and the diversity of the microbial community were investigated during the experimental period of 40 days. The results showed that 84.17–89.97% of nitrogen input was removed in all the treatments, residual nitrogen was higher in the glucose treatments. Lower inorganic nitrogen at a higher C/N ratio was obtained with the addition of the same carbon source due to more assimilation. Among all, the citrate treatment at C/N 12 obtained the best control in inorganic nitrogen concentrations and better in biofloc concentration owing to efficient dissimilation and assimilation. Moreover, from day 26 to day 40, the number of detected OTUs increased by 22.90–58.40% while the Shannon indices have not changed much in all the treatments. Ten of the top 15 genera were the typical denitrifying genera in each treatment, the total abundance of these decreased by 7.00% to 58.00% while that of Paracoccus, as one of the denitrifiers added, increased by 3.00% to 25.00%. This suggested that the addition of citrate at higher C/N could improve the denitrification function of biofloc system.

中文翻译：

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接种硝化菌和好氧反硝化菌的异地生物絮团系统中碳源和碳氮比对微生物群落和功能的影响

为了控制生物絮团系统中无机氮和生物絮团的浓度，需要加强硝化和反硝化脱氮。本研究在养殖废水中接种硝化菌和好氧反硝化菌，启动后每天输入氮​​16.80 mg/L，在9和12添加葡萄糖和柠檬酸C/N，不添加碳源作为控制（C/N 6.17）。在40天的试验期内，对无机氮、总氮和生物絮团的浓度以及微生物群落的多样性进行了调查。结果表明，所有处理均去除了84.17-89.97%的氮输入，葡萄糖处理的残留氮较高。由于更多的同化作用，添加相同的碳源可以获得更高 C/N 比的更低无机氮。其中，C/N 12 柠檬酸盐处理由于有效的异化和同化作用，对无机氮浓度的控制效果最好，对生物絮团浓度的控制效果更好。此外，从第 26 天到第 40 天，检测到的 OTU 数量增加了 22.90-58.40%，而香农指数在所有处理中都没有太大变化。前15个属中有10个属各处理典型反硝化属，总丰度下降7.00%～58.00%，而 由于高效的异化和同化作用，C/N 12 柠檬酸盐处理获得了对无机氮浓度的最佳控制和更好的生物絮团浓度。此外，从第 26 天到第 40 天，检测到的 OTU 数量增加了 22.90-58.40%，而香农指数在所有处理中都没有太大变化。前15个属中有10个属各处理典型反硝化属，总丰度下降7.00%～58.00%，而 由于高效的异化和同化作用，C/N 12 柠檬酸盐处理获得了对无机氮浓度的最佳控制和更好的生物絮团浓度。此外，从第 26 天到第 40 天，检测到的 OTU 数量增加了 22.90-58.40%，而香农指数在所有处理中都没有太大变化。前15个属中有10个属各处理典型反硝化属，总丰度下降7.00%～58.00%，而副球菌作为添加的反硝化剂之一，增加了 3.00% 至 25.00%。这表明在较高的 C/N 下添加柠檬酸盐可以提高生物絮团系统的反硝化功能。