Table_2_Water Treatment Effect, Microbial Community Structure, and Metabolic Characteristics in a Field-Scale Aquaculture Wastewater Treatment System.xlsx

Avoiding and mitigating the introduction of harmful effluent into the environment must be a key part of intensive industrial aquaculture development in order to minimize pollution impacts. We constructed a novel field-scale aquaculture wastewater treatment system (FAWTS) involving three-stage purification to efficiently remove nutrients from effluent wastewater. However, the mechanisms of nutrient attenuation in the FAWTS are still unclear. Since microbiota play an important role in the treatment of aquatic pollutants, we hypothesized that the different stages of FAWTS may have enriched various nutrient-metabolizing bacteria, with these promoting nutrient attenuation. We therefore tested microbial metabolic activity, microbial composition, and their metabolic potential using Biolog-GN2 microplate culture and high-throughput sequencing of prokaryotic 16S rRNA gene amplicons. Our results showed that the FAWTS displayed high removal efficiencies for chemical oxygen demand (COD, 74.4–91.2%), total nitrogen (TN, 66.9–86.8%), and total phosphorus (TP, 76.2–95.9%). Simultaneously, microbial metabolic activity for various carbon sources was significantly enhanced in FAWTS biofilms. Denitrifying and phosphorus-removing bacteria such as Rhodobacter were enriched in these biofilms, and genes participating in denitrification and the pathway from methylphosphonate to α-D-ribose-1,5-bisphosphate were increased in the biofilm communities. These results imply that the transformed multistep purification system effectively removed N, P, and COD from aquaculture wastewater by enhancing the bacterial communities involved in these processes. This suggests that contamination-free aquaculture is a feasible goal, and that microbial communities are central to pollutant removal.

避免有害废水排入环境并减轻其污染影响，需作为集约化工业水产养殖发展的核心环节，以最大限度降低污染危害。我们构建了一种新型现场规模水产养殖废水处理系统（field-scale aquaculture wastewater treatment system, FAWTS），采用三级净化工艺以高效去除养殖废水中的营养物质。然而，该系统内营养物质消减的具体机制仍不明确。鉴于微生物群落在水生污染物治理中发挥关键作用，我们推测FAWTS的不同净化工段可能富集了各类营养物质代谢细菌，从而推动营养物质的消减过程。为此，我们通过Biolog-GN2微孔板培养技术以及原核生物16S rRNA基因扩增子高通量测序，对微生物代谢活性、群落组成及其代谢潜力进行了检测。研究结果表明，FAWTS对化学需氧量（chemical oxygen demand, COD）、总氮（total nitrogen, TN）与总磷（total phosphorus, TP）均表现出优异的去除效率，去除率分别为74.4%~91.2%、66.9%~86.8%及76.2%~95.9%。与此同时，FAWTS生物膜对多种碳源的微生物代谢活性显著提升。反硝化与除磷细菌如红杆菌属（Rhodobacter）在该生物膜中得以富集，且参与反硝化作用以及甲基膦酸酯转化为α-D-核糖-1,5-二磷酸通路的相关基因，在生物膜群落中的丰度显著升高。上述结果表明，改造后的多级净化系统可通过强化参与上述过程的细菌群落，有效去除水产养殖废水中的氮、磷及化学需氧量。这提示实现无污染水产养殖是可行目标，而微生物群落正是污染物去除的核心所在。