Abstract：
Further reducing total nitrogen (TN) and total phosphorus (TP) in the secondary effluent needs to be realized effectively and in an eco-friendly manner. Herein, four pyrite/sawdust composite-based biofilters were established to treat simulated secondary effluent for 304 days. The results demonstrated that effluent TN and TP concentrations from biofilters under the optimal hydraulic retention time (HRT) of 3.5 h were stable at <2.0 and 0.1 mg/L, respectively, and no significant differences were observed between inoculated sludge sources. The pyrite/sawdust composite-based biofilters had low N2O, CH4, and CO2 emissions, and the effluent\'s DOM was mainly composed of five fluorescence components. Moreover, mixotrophic denitrifiers (Thiothrix) and sulfate-reducing bacteria (Desulfosporosinus) contributing to microbial nitrogen and sulfur cycles were enriched in the biofilm. Co-occurrence network analysis deciphered that Chlorobaculum and Desulfobacterales were key genera, which formed an obvious sulfur cycle process that strengthened the denitrification capacity. The higher abundances of genes encoding extracellular electron transport (EET) chains/mediators revealed that pyrite not only functioned as an electron conduit to stimulate direct interspecies electron transfer by flagella but also facilitated EET-associated enzymes for denitrification. This study comprehensively evaluates the water-gas-biofilm phases of pyrite/sawdust composite-based biofilters during a long-term study, providing an in-depth understanding of boosted electron transfer in pyrite-based mixotrophic denitrification systems.
摘要：
进一步降低二级流出物中的总氮(TN)和总磷(TP)需要以生态友好的方式有效地实现。在这里，建立了四个基于黄铁矿/锯末复合材料的生物滤池，以处理模拟的二级废水304天。结果表明，在3.5h的最佳水力停留时间（HRT）下，生物滤池的出水TN和TP浓度稳定在<2.0和0.1mg/L。分别,接种污泥源之间没有显着差异。黄铁矿/锯末复合生物滤池具有较低的N2O，CH4和CO2排放，出水DOM主要由5种荧光成分组成。此外，促进微生物氮和硫循环的兼养反硝化菌（Thiothrix）和硫酸盐还原菌（Desulfosporosinus）富集在生物膜中。共现网络分析破译了绿藻和脱硫杆菌是关键属，形成了明显的硫循环过程,增强了脱氮能力。编码细胞外电子传递（EET）链/介体的基因的丰度较高，表明黄铁矿不仅充当电子导管，可以刺激鞭毛的直接种间电子传递，而且还促进了EET相关酶的反硝化。这项研究在长期研究中全面评估了黄铁矿/锯末复合材料基生物过滤器的水气生物膜相，深入了解基于黄铁矿的混合营养反硝化系统中增强的电子转移。
