In this study, a pilot-scale two-stage denitrification filter (TSDNF) was developed to further remove the effluent nitrate from a cyclic activated sludge system. Sponge iron and volcanic rock were used as DNF-1 and DNF-2 filter beds, respectively. A single-stage DNF-3 filter with volcanic rock was used as the control. Most dissolved oxygen (DO) was consumed for iron oxidation in the DNF-1, and in turn denitrification rates increased in the DNF-2. In the DNF-1, 17.9 %±13.6 % of the NO₃⁻-N was removed in the absence of organic carbons, resulting in a significant increase in the total NO₃⁻-N removal in the TSDNF with a COD/NO₃⁻-N ratio of about 2.6. Autotrophic denitrification should be finished by the dominant Fe(II)-oxidizing nitrate-reducing Gallionellaceae genus (21.38 %) in the DNF-1, while common denitrifying strains were dominant in both DNF-2 and DNF-3. Moreover, obvious chemical phosphorus removal (83.3 %) was found in the DNF-1. Therefore, simultaneous autotrophic denitrification and chemical P-removal can be achieved using iron ions released from sponge iron filters, which provides a new model to reshape the design of advanced removal of nitrogen and phosphorus in the secondary clarifier effluent.

在这项研究中，开发了中试规模的两级反硝化过滤器（TSDNF），以进一步从循环活性污泥系统中去除废水中的硝酸盐。海绵铁和火山岩分别用作DNF-1和DNF-2滤床。带有火山岩的单级DNF-3过滤器用作对照。DNF-1中的铁氧化消耗了大部分溶解氧（DO），而DNF-2中反硝化速率增加了。在DNF-1中，在不存在有机碳的情况下，NO ₃ ^-- N的去除量为17.9％±13.6％，这导致使用COD / NO ₃的TSDNF中总NO ₃ ^-- N的去除量显着增加。^--N比约为2.6。自养反硝化作用应通过DNF-1中占主导地位的Fe（II）-氧化性硝酸盐还原菌（21.38％）来完成，而常见的反硝化菌株在DNF-2和DNF-3中均占优势。此外，在DNF-1中发现了明显的化学除磷（83.3％）。因此，利用海绵铁滤池释放的铁离子可以实现自养反硝化和化学除磷的同时，这提供了一个新的模型，可以重塑二次澄清池废水中氮和磷的先进去除设计。