Abstract Stringent environmental legislation in Europe, especially in the Baltic Sea area, limits the discharge of nutrients to natural water bodies, limiting the aquaculture production in the region. Therefore, cost-efficient end-of-pipe treatment technologies to reduce nitrogen (N) discharge are required for the sustainable growth of marine land-based RAS. The following study examined the potential of fed batch reactors (FBR) in treating saline RAS effluents, aiming to define optimal operational conditions and evaluate the activated sludge denitrification capacity using external (acetate, propionate and ethanol) and internal carbon sources (RAS fish organic waste (FOW) and RAS fermented fish organic waste (FFOW)). The results show that between the evaluated operation cycle times (2, 4, and 6 h), the highest nitrate/nitrite removal rate was achieved at an operation cycle time of 2 h (corresponding to a hydraulic retention time of 2.5 h) when acetate was used as a carbon source. The specific denitrification rates were 98.7 ± 3.4 mg NO3−-N/(h g biomass) and 93.2 ± 13.6 mg NOx−-N/(h g biomass), with a resulting volumetric denitrification capacity of 1.20 kg NO3−-N/(m3 reactor d). The usage of external and internal carbon sources at an operation cycle time of 4 h demonstrated that acetate had the highest nitrate removal rate (57.6 ± 6.6 mg N/(h g biomass)), followed by propionate (37.5 ± 6.3 mg NO3−-N/(h g biomass)), ethanol (25.5 ± 6.0 mg NO3−-N/(h g biomass)) and internal carbon sources (7.7 ± 1.6–14.1 ± 2.2 mg NO3−-N/(h g biomass)). No TAN (Total Ammonia Nitrogen) or PO43- accumulation was observed in the effluent when using the external carbon sources, while 0.9 ± 0.5 mg TAN/L and 3.9 ± 1.5 mg PO43--P/L was found in the effluent when using the FOW, and 8.1±0.7 mg TAN/L and 7.3 ± 0.9 mg PO43--P/L when using FFOW. Average sulfide concentrations varied between 0.002 and 0.008 mg S2-/L when using the acetate, propionate and FOW, while using ethanol resulted in the accumulation of sulfide (0.26 ± 0.17 mg S2-/L). Altogether, it was demonstrated that FBR has a great potential for end-of-pipe denitrification in marine land-based RAS, with a reliable operation and a reduced reactor volume as compared to the other available technologies. Using acetate, the required reactor volume is less than half of what is needed for other evaluated carbon sources, due to the higher denitrification rate achieved. Additionally, combined use of both internal and external carbon sources would further reduce the operational carbon cost.

中文翻译：

---

使用外部和内部碳源的海洋再循环水产养殖系统废水中的活性污泥脱氮

摘要 欧洲严格的环境立法，特别是波罗的海地区，限制了营养物质向天然水体的排放，限制了该地区的水产养殖生产。因此，海洋陆基 RAS 的可持续发展需要具有成本效益的末端处理技术来减少氮 (N) 排放。以下研究检验了分批补料反应器 (FBR) 在处理含盐 RAS 流出物方面的潜力，旨在确定最佳操作条件并评估使用外部（乙酸盐、丙酸盐和乙醇）和内部碳源（RAS 鱼有机废物）的活性污泥脱氮能力(FOW) 和 RAS 发酵鱼有机废物 (FFOW)）。结果表明，在评估的操作周期时间（2、4 和 6 小时）之间，当使用乙酸盐作为碳源时，在 2 小时的操作循环时间（对应于 2.5 小时的水力停留时间）下，硝酸盐/亚硝酸盐去除率最高。比反硝化率为 98.7 ± 3.4 mg NO3--N/(hg 生物量) 和 93.2 ± 13.6 mg NOx--N/(hg 生物量)，产生的体积反硝化能力为 1.20 kg NO3--N/(m3 反应器d)。在 4 小时的运行周期内使用外部和内部碳源表明，醋酸盐的硝酸盐去除率最高（57.6 ± 6.6 mg N/（hg 生物量）），其次是丙酸盐（37.5 ± 6.3 mg NO3−-N） /（hg 生物量））、乙醇（25.5 ± 6.0 mg NO3−-N/（hg 生物量））和内部碳源（7.7 ± 1.6–14.1 ± 2.2 mg NO3−-N/（hg 生物量））。使用外部碳源时，在流出物中未观察到 TAN（总氨氮）或 PO43- 积累，而使用外部碳源时在流出物中发现 0.9 ± 0.5 mg TAN/L 和 3.9 ± 1.5 mg PO43--P/L FOW，使用 FFOW 时为 8.1±0.7 mg TAN/L 和 7.3 ± 0.9 mg PO43--P/L。使用醋酸盐、丙酸盐和 FOW 时，平均硫化物浓度在 0.002 和 0.008 毫克 S2-/L 之间变化，而使用乙醇会导致硫化物积累（0.26 ± 0.17 毫克 S2-/L）。总而言之，事实证明，与其他可用技术相比，FBR 在海洋陆基 RAS 中具有巨大的管道末端反硝化潜力，具有可靠的运行和减少的反应器体积。使用醋酸盐，所需的反应器体积不到其他评估碳源所需的一半，由于达到了更高的反硝化率。此外，内部和外部碳源的结合使用将进一步降低运营碳成本。