Department of Civil and Environmental Engineering, Pusan National University, Busan 46241, Republic of Korea.
Korea Testing & Research Institute, Ulsan 44412, Republic of Korea.
Sci Total Environ. 2021 Mar 1;758:143677. doi: 10.1016/j.scitotenv.2020.143677. Epub 2020 Nov 27.
Removal of nitrogen compounds is particularly important domestic wastewater treatment. Our recent study reported the successful removal of nitrogen in single-chamber electroactive biofilm reactors (EBRs) under aeration-free conditions. We hypothesized that the oxygen diffused from the air-cathode is a key factor in the removal of nitrogen in the EBR. If so, the effect of the penetrated oxygen would vary according to the ratio of the air-cathode surface area to the reactor volume (AV ratio) and the hydraulic retention time (HRT). In this study, single-chamber EBRs with three different AV ratios: 125 m/m (EBR-125), 250 m/m (EBR-250), and 500 m/m (EBR-500) were evaluated for the removal of nitrogen under different HRTs of 0.5-6 h. The higher the AV ratio, the greater the increase in nitrification. The total nitrogen (TN) removal efficiency of EBR-125 and EBR-250 decreased as the HRT decreased, while that of EBR-500 increased. EBR-250 showed the highest TN removal (62.0%) with well-balanced nitrification (83.9%) and denitrification (75.1%) at an HRT of 6 h. However, EBR-500 appeared to be superior for practical application because it showed a comparable TN removal (59%) at a substantially short HRT of 1 h. The microbial communities that were involved in the nitrogen cycle varied according to whether the biofilms were located on the anodes, separators, and cathodes but were similar among EBRs with different AV ratios. Nitrifying bacteria were detected in the biofilms that were presented on the cathodes (approximately 7.8% of the total phylotypes), while denitrifying bacteria were mainly found in biofilm that were located on the anodes (approximately 23.3%). Anammox bacteria were also detected on the anode (approximately 3.7%) and in the separator biofilms (approximately 1.9%) of all the EBRs. These results suggest that both the A/V ratio and the HRT could affect the counter diffusion of substrates (NH and organic compounds) and oxygen in the biofilms and allow interactions between a diversity of microorganisms for the successful removal of nitrogen in EBRs. These findings are expected to aid in the development of new applications using EBR for energy-saving wastewater treatment.
去除氮化合物在污水处理中尤为重要。我们最近的研究报告称，在无曝气条件下，单室电活性生物膜反应器（EBR）成功去除了氮。我们假设从空气阴极扩散的氧气是 EBR 中去除氮的关键因素。如果是这样，穿透氧的效果会根据空气阴极表面积与反应器体积之比（A/V 比）和水力停留时间（HRT）而变化。在这项研究中，使用三种不同的 A/V 比（125 m/m（EBR-125）、250 m/m（EBR-250）和 500 m/m（EBR-500））的单室 EBR 在 0.5-6 h 的不同 HRT 下评估了去除氮的效果。A/V 比越高，硝化作用的增加就越大。EBR-125 和 EBR-250 的总氮（TN）去除效率随着 HRT 的降低而降低，而 EBR-500 的去除效率则增加。在 HRT 为 6 h 时，EBR-250 表现出最高的 TN 去除率（62.0%），同时硝化（83.9%）和反硝化（75.1%）平衡良好。然而，EBR-500 似乎更适合实际应用，因为它在 HRT 短得多的 1 h 时表现出相当的 TN 去除率（59%）。参与氮循环的微生物群落因生物膜位于阳极、分离器和阴极而有所不同，但在不同 A/V 比的 EBR 中相似。在阴极上的生物膜中检测到硝化细菌（约占总类群的 7.8%），而反硝化细菌主要存在于阳极上的生物膜中（约占 23.3%）。在所有的 EBR 中，还在阳极（约 3.7%）和分离器生物膜（约 1.9%）上检测到厌氧氨氧化菌。这些结果表明，A/V 比和 HRT 都可以影响生物膜中基质（NH 和有机化合物）和氧气的反向扩散，并允许各种微生物之间的相互作用，从而成功地在 EBR 中去除氮。这些发现有望为使用 EBR 进行节能废水处理的新应用提供帮助。
