College of Environmental Science and Engineering, Donghua University, Shanghai, 201620, China.
College of Environmental Science and Engineering, Tongji University, Shanghai, 200092, China.
Chemosphere. 2023 Oct;337:139352. doi: 10.1016/j.chemosphere.2023.139352. Epub 2023 Jun 30.
Fe-mediated autotrophic denitrification (ADN) can be suppressed by iron oxide coverage resulting from Fe corrosion. The mixotrophic denitrification (MDN) coupling Fe-mediated ADN with heterotrophic denitrification (HDN) can circumvent the weakening of Fe-mediated ADN over operation time. But the interaction between HDN and Fe-mediated ADN for nitrogen removal of secondary effluent with deficient bioavailable organics remains unclear. When the influent COD/NO-N ratio increased from 0.0 to 1.8-2.1, the TN removal efficiency was promoted significantly. The increased carbon source did not inhibit ADN, but promoted ADN and HDN synchronously. The formation of extracellular polymeric substances (EPS) was also facilitated concomitantly. Protein (PN) and humic acid (HA) in EPS increased significantly, which capable of accelerating electron transfer of denitrification. Due to that the electron transfer of HDN occurs intracellularly, the EPS with the capacity of accelerating electron transfer had a negligible influence on HDN. But for Fe-mediated ADN, the increased EPS as well as corresponding PN and HA facilitated TN and NO-N removal significantly, while accelerated the electron release originating from Fe corrosion. The bioorganic-Fe complexes were generated on Fe surface after used, meaning that the soluble EPS and soluble microbial products (SMP) participated in the electron transfer of Fe-mediated ADN. The coexistence of HDN and ADN denitrifiers demonstrated the synchronous enhancement of HDN and ADN by the external carbon source. From the perspective of EPS and related SMP, the insight of enhancing Fe-mediated ADN by external carbon source is beneficial to implement high-efficiency MDN for organics-deficient secondary wastewater.
铁介导的自养反硝化（ADN）会被铁腐蚀导致的氧化铁覆盖所抑制。混合自养反硝化（MDN）将铁介导的 ADN 与异养反硝化（HDN）相结合，可以避免铁介导的 ADN 在运行过程中减弱。但是，对于缺乏生物可利用有机物的二级出水，HDN 与铁介导的 ADN 之间的相互作用对于氮去除仍不清楚。当进水 COD/NO-N 比从 0.0 增加到 1.8-2.1 时，TN 去除效率显著提高。增加的碳源并没有抑制 ADN，而是同时促进了 ADN 和 HDN。同时也促进了胞外聚合物物质（EPS）的形成。EPS 中的蛋白质（PN）和腐殖酸（HA）显著增加，这能够加速反硝化的电子转移。由于 HDN 的电子转移发生在细胞内，因此具有加速电子转移能力的 EPS 对 HDN 的影响可以忽略不计。但是对于铁介导的 ADN，增加的 EPS 以及相应的 PN 和 HA 显著促进了 TN 和 NO-N 的去除，同时加速了源自铁腐蚀的电子释放。使用后，Fe 表面生成了生物有机-Fe 配合物，这意味着可溶性 EPS 和可溶性微生物产物（SMP）参与了铁介导的 ADN 的电子转移。HDN 和 ADN 反硝化菌的共存证明了外加碳源对 HDN 和 ADN 的同步增强。从 EPS 和相关 SMP 的角度来看，外加碳源增强铁介导的 ADN 的见解有利于实施高效的有机物缺乏的二级废水的 MDN。
