Limited simultaneous nitrification-denitrification (SND) in aerobic granular sludge systems treating municipal wastewater: Mechanisms and practical implications
Limited simultaneous nitrification-denitrification (SND) in aerobic granular sludge systems treating municipal wastewater: Mechanisms and practical implications
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DOI：
10.1016/j.wroa.2020.100048
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发表时间：
2020-05-01
期刊：
影响因子：
7.5
通讯作者：
Derlon, Nicolas
中科院分区：
文献类型：
--
作者：
Layer, Manuel;Villodres, Mercedes Garcia;Derlon, Nicolas
同时硝化反硝化（SND），从理论上讲，好氧颗粒污泥系统比传统的活性污泥系统的一个关键优势。但实践经验和文献表明，在使用AGS系统处理城市污水时，SND和总氮去除是有限的。因此，本研究旨在量化好氧颗粒污泥（AGS）系统处理城市污水过程中SND的程度和机制。实验（长期和批量测试）以及数学建模。我们的实验结果表明，在用AGS系统处理低强度城市污水时，SND明显有限（14e39%），而在处理仅含有扩散底物（90%）的合成进水时，可以观察到几乎完全的SND。我们的模拟表明，限制SND背后的主要机制是：(1)颗粒内部缺氧区形成的动力学，(2)这些区域中电子给体的扩散性和可用性，以及(3)曝气模式。缺氧区的发展是由颗粒上层氧气的利用驱动的，导致颗粒内氧气的运输限制；这种效果与颗粒大小和废水成分密切相关。对于体积溶解氧（DO）浓度为2mgo2 L1的恒定曝气条件下的小颗粒，好氧阶段缺氧带的发展是有限的，而对于大颗粒，缺氧带仅在曝气阶段的短时间内发展。模拟结果进一步表明，很大一部分电子供体实际上是在体或颗粒表面的有氧氧化还原区而不是缺氧氧化还原区使用的。因此，如果在曝气阶段保持恒定的DO，则AGS处理低强度城市污水无法实现完全SND。因此需要优化通气策略。利用数学模型成功地测试了两步和交替曝气，在不影响硝化作用的情况下，将TN去除率提高到40e79%，并将电子供体利用转向缺氧氧化还原条件。(c) 2020作者。Elsevier Ltd.出版。这是一篇基于CC BY许可（http://creativecommons.org/licenses/by/4.0/）的开放获取文章。
Simultaneous nitrification-denitrification (SND) is, in theory, a key advantage of aerobic granular sludge systems over conventional activated sludge systems. But practical experience and literature suggests that SND and thus total nitrogen removal are limited during treatment of municipal wastewater using AGS systems. This study thus aims at quantifying the extent and understanding the mechanisms of SND during treatment of municipal wastewater with aerobic granular sludge (AGS) systems. Experiments (long-term and batch-tests) as well as mathematical modelling were performed. Our experimental results demonstrate that SND is significantly limited during treatment of low-strength municipal wastewater with AGS systems (14e39%), while almost full SND is observed when treating synthetic influent containing only diffusible substrate (90%). Our simulations demonstrate that the main mechanisms behind limited SND are (1) the dynamics of anoxic zone formation inside the granule, (2) the diffusibility and availability of electron-donors in those zones and (3) the aeration mode. The development of anoxic zones is driven by the utilisation of oxygen in the upper layers of the granule leading to transport limitations of oxygen inside the granule; this effect is closely linked to granule size and wastewater composition. Development of anoxic zones during the aerobic phase is limited for small granules at constant aeration at bulk dissolved oxygen (DO) concentration of 2 mgO2 L1, and anoxic zones only develop during a brief period of the aerated phase for large granules. Modelling results further indicate that a large fraction of electron-donors are actually utilised in aerobic rather than anoxic redox zones e in the bulk or at the granule surface. Thus, full SND cannot be achieved with AGS treating low strength municipal wastewater if a constant DO is maintained during the aeration phase. Optimised aeration strategies are therefore required. 2-step and alternating aeration are tested successfully using mathematical modelling and increase TN removal to 40e79%, without compromising nitrification, and by shifting electron-donor utilisation towards anoxic redox conditions. (c) 2020 The Authors. Published by Elsevier Ltd. This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/4.0/).