Abstract：
Iron-based ecological floating beds (EFBs) are often used to treat the secondary effluent from wastewater treatment plant to enhance the denitrification process. However, the impact and necessity of plants on iron-based EFBs have not been systematically studied. In this research, two iron-based EFBs with and without plants (EFB-P and EFB) were performed to investigate the response of plants on nutrient removal, GHG emissions, microbial communities and functional genes. Results showed the total nitrogen and total phosphorus removal in EFB-P was 45-79% and 48-72%, respectively, while that in EFB was 31-67% and 44-57%. Meanwhile, plants could decrease CH4 emission flux (0-3.89 mg m-2 d-1) and improve CO2 absorption (4704-22321 mg m-2 d-1). Plants could increase the abundance of Nitrosospira to 1.6% which was a kind of nitrifying bacteria dominant in plant rhizosphere. Among all denitrification related genera, Simplicispira (13.08%) and Novosphingobium (6.25%) accounted for the highest proportion of plant rhizosphere and iron scrap, respectively. Anammox bacteria such as Candidatus_Brocadia was more enriched on iron scraps with the highest proportion was 1.21% in EFB-P, and 2.20% in EFB. Principal co-ordinates analysis showed that plants were the critical factor determining microbial community composition. TN removal pathways were mixotrophic denitrification and anammox in EFB-P while TP removal pathways were plant uptake and phosphorus-iron coprecipitation. In general, plants play an important directly or indirectly role in iron-based EFBs systems, which could not only improve nutrients removal, but also minimize the global warming potential and alleviate the greenhouse effect to a certain extent.
摘要：
铁基生态浮床（EFBs）通常用于处理污水处理厂的二级出水，以增强反硝化过程。然而,植物对铁基EMBs的影响和必要性尚未得到系统研究。在这项研究中,有和没有植物的两个铁基EFB（EFB-P和EFB）进行了研究植物对养分去除的反应，温室气体排放，微生物群落和功能基因。结果表明，EFB-P的总氮和总磷去除率分别为45-79％和48-72％，分别,而EFB的比例为31-67%和44-57%。同时,植物可以降低CH4排放通量（0-3.89mgm-2d-1）并改善CO2吸收（4704-223221mgm-2d-1）。植物可以将亚硝基螺旋体的丰度提高到1.6％，这是一种在植物根际中占主导地位的硝化细菌。在所有反硝化相关的属中，植物根际和铁屑中占比例最高的是单壁(13.08%)和新鞘(6.25%),分别。Anammox细菌如Candidatus_Brocadia在铁屑上更富集，在EFB-P中比例最高，为1.21%，和2.20%的EFB。主坐标分析表明，植物是决定微生物群落组成的关键因素。EFB-P中的TN去除途径为混合营养反硝化和厌氧氨氧化，而TP去除途径为植物吸收和磷-铁共沉淀。总的来说,植物在铁基EFBs系统中起着直接或间接的重要作用，这不仅可以提高营养物质的去除，而且还可以最大程度地减少全球变暖的潜力，并在一定程度上缓解温室效应。
