Chemical Engineering Department, Universidad de Alcalá, Alcalá de Henares, Spain; IMDEA Agua, Parque Tecnológico de la Universidad de Alcalá, 28805, Alcalá de Henares, Spain.
Department of Biology, Aarhus University, Ole Worms Allé 1, 8000 Aarhus C, Denmark; WATEC, Aarhus University, Ny Munkegade 120, 8000 Aarhus C, Denmark.
Sci Total Environ. 2020 Sep 15;735:139522. doi: 10.1016/j.scitotenv.2020.139522. Epub 2020 May 21.
Constructed wetlands are an effective biofilter-based technology for treating wastewater in a sustainable way; however, their main disadvantage is a large area footprint. To cope with this limitation a new generation of constructed wetlands, the METlands®, have been recently reported. METlands® replace gravel with a granular electrically conductive material to enhance the oxidative metabolisms of electroactive bacteria by facilitating the flux of electron through the material and, consequently, increase bioremediation rates. In this work we evaluated the performance of a new electron sink (e-sink) device with the purpose of controlling and enhancing the electrochemical consumption of electrons from microbial metabolism without energy consumption. The e-sink device was integrated inside the biofilter bed and was tested using different electron acceptors with high redox potentials, like oxygen and hypochlorite. Interestingly, the presence of the e-sink allowed novel redox gradients to form inside the METland® and, consequently, a new electron flow was demonstrated by measuring both the electric potential and current density profiles of the bed. Three independent biofilters were constructed and operated under flooded conditions. Ec-coke and electroconductive biochar (ec-biochar) were used as electrically conductive bed materials, while gravel was used as an inert control. Furthermore, e-sink integration inside the electrically conductive bed outperformed METlands® for removing pollutants, already much more efficient than standard gravel biofilters. COD removal was increased from 90% in METland® to 95% in the e-sink METland® as compared to 75% for the control, while total nitrogen removal was enhanced from 64% in METland® to 71% in e-sink METland® as compared to 55% for the control. Our results indicate that increasing the electrochemical availability of electron acceptors by using the e-sink will be a suitable method for controlling the electron flow inside the filter bed and can be integrated in full scale METlands® for achieving high removal rates.
人工湿地是一种有效的基于生物过滤的废水处理技术，可持续处理废水；然而，它们的主要缺点是占地面积大。为了应对这一限制，最近报道了新一代人工湿地，即 METlands®。METlands®用一种颗粒状导电材料替代砾石，通过促进电子通过材料的流动，增强电活性细菌的氧化代谢，从而提高生物修复速率。在这项工作中，我们评估了一种新型电子汇流排（e-sink）装置的性能，目的是在不消耗能量的情况下控制和增强微生物代谢中电子的电化学消耗。e-sink 装置集成在生物滤床内部，并使用具有高氧化还原电位的不同电子受体（如氧气和次氯酸盐）进行了测试。有趣的是，e-sink 的存在允许在 METland®内部形成新的氧化还原梯度，并且通过测量床的电势和电流密度分布来证明新的电子流动。构建了三个独立的生物滤池，并在淹没条件下运行。Ec-coke 和导电生物炭（ec-biochar）被用作导电床材料，而砾石被用作惰性对照。此外，与标准砾石生物滤池相比，将 e-sink 集成到导电床中可以提高污染物的去除效率，已经比 METlands®更高效。与对照相比，METland®中的 COD 去除率从 90%提高到 e-sink METland®中的 95%，而总氮去除率从 METland®中的 64%提高到 e-sink METland®中的 71%，而对照中的总氮去除率为 55%。我们的结果表明，通过使用 e-sink 增加电子受体的电化学可用性将是控制过滤床内电子流动的一种合适方法，并可集成在全规模的 METlands®中，以实现高去除率。
