Labile carbon release from oxic–anoxic cycling in woodchip bioreactors enhances nitrate removal without increasing nitrous oxide accumulation
Labile carbon release from oxic–anoxic cycling in woodchip bioreactors enhances nitrate removal without increasing nitrous oxide accumulation
复制标题
木片生物反应器中的有氧缺氧循环释放的不稳定碳可增强硝酸盐的去除，而不增加一氧化二氮的积累
DOI：
10.1039/d1ew00446h
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发表时间：
2021
期刊：
影响因子：
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通讯作者：
Reid, Matthew C.
中科院分区：
文献类型：
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作者：
McGuire, Philip M.;Dai, Valentina;Walter, M. Todd;Reid, Matthew C.
由于木质纤维素木片生物质中碳 (C) 的顽固性，处理农业排水和径流的木片生物反应器 (WBR) 中的反硝化通常受到碳限制。最近的研究表明，通过定期排水和重新淹没 WBR 实现的氧化还原波动可以通过增强好氧期间不稳定 C 的释放来提高硝酸盐去除率。虽然染色-再润湿 (DRW) 循环似乎对提高反硝化 WBR 的性能有着巨大的希望，但富氮环境中的氧化还原波动通常与温室气体一氧化二氮 (N2O) 排放的增加有关，因为微需氧条件下抑制了 N2O 还原。在这里，我们评估了与 DRW 相关的氧化缺氧循环对 20°C 下一组互补的流通式和批量实验室生物反应器中从木片中动员的 C 的数量和质量、硝酸盐去除率和 N2O 积累的影响。氧化还原波动显着提高了硝酸盐去除率，从连续饱和 (CS) 反应器中的 4.8–7.2 g N m−3 d−1 到反应器排空并重新饱和后 24 小时内的 9.8–11.2 g N m−3 d−1 。结果支持这样的理论，即 DRW 条件通过增加木片中不稳定有机碳的动员来提高 NO3− 去除率，同时好氧缺氧反应器溶解碳池中的芳香度较低，凸显了木质素分解对总体碳释放的重要性。与连续饱和反应器相比，没有证据表明 DRW 反应器中 N2O 积累量更大（以 N2O 产物产率衡量）。我们认为，在有氧期后，N2O 还原剂的有机 C 利用率大于微需氧抑制 N2O 还原在控制 N2O 动力学方面的作用。讨论了这些发现对于优化 DRW 循环以提高反硝化 WBR 中硝酸盐去除率的影响。
Denitrification in woodchip bioreactors (WBRs) treating agricultural drainage and runoff is frequently carbon-limited due to the recalcitrance of carbon (C) in lignocellulosic woodchip biomass. Recent research has shown that redox fluctuations, achieved through periodic draining and re-flooding of WBRs, can increase nitrate removal rates by enhancing the release of labile C during oxic periods. While dying–rewetting (DRW) cycles appear to hold great promise for improving the performance of denitrifying WBRs, redox fluctuations in nitrogen-rich environments are commonly associated with enhanced emissions of the greenhouse gas nitrous oxide (N2O) due to inhibition of N2O reduction in microaerophilic conditions. Here, we evaluate the effects of oxic–anoxic cycling associated with DRW on the quantity and quality of C mobilized from woodchips, nitrate removal rates, and N2O accumulation in a complementary set of flow-through and batch laboratory bioreactors at 20 °C. Redox fluctuations significantly increased nitrate removal rates from 4.8–7.2 g N m−3 d−1 in a continuously saturated (CS) reactor to 9.8–11.2 g N m−3 d−1 24 h after a reactor is drained and re-saturated. Results support the theory that DRW conditions lead to faster NO3− removal rates by increasing mobilization of labile organic C from woodchips, with lower aromaticity in the dissolved C pool of oxic–anoxic reactors highlighting the importance of lignin breakdown to overall carbon release. There was no evidence for greater N2O accumulation, measured as N2O product yields, in the DRW reactors compared to continuously saturated reactors. We propose that greater organic C availability for N2O reducers following oxic periods outweighs the effect of microaerophilic inhibition of N2O reduction in controlling N2O dynamics. Implications of these findings for optimizing DRW cycling to enhance nitrate removal rates in denitrifying WBRs are discussed.