Australian Centre for Water and Environmental Biotechnology, Faculty of Engineering, Architecture and Information Technology, The University of Queensland, St Lucia, Queensland, Australia.
Australian Centre for Water and Environmental Biotechnology, Faculty of Engineering, Architecture and Information Technology, The University of Queensland, St Lucia, Queensland, Australia.
Water Res. 2023 May 15;235:119887. doi: 10.1016/j.watres.2023.119887. Epub 2023 Mar 16.
Nitrate contamination has been commonly detected in water environments and poses serious hazards to human health. Previously methane was proposed as a promising electron donor to remove nitrate from contaminated water. Compared with pure methane, natural gas, which not only contains methane but also other short chain gaseous alkanes (SCGAs), is less expensive and more widely available, representing a more attractive electron source for removing oxidized contaminants. However, it remains unknown if these SCGAs can be utilized as electron donors for nitrate reduction. Here, two lab-scale membrane biofilm reactors (MBfRs) separately supplied with propane and butane were operated under oxygen-limiting conditions to test its feasibility of microbial nitrate reduction. Long-term performance suggested nitrate could be continuously removed at a rate of ∼40-50 mg N/L/d using propane/butane as electron donors. In the absence of propane/butane, nitrate removal rates significantly decreased both in the long-term operation (∼2-10 and ∼4-9 mg N/L/d for propane- and butane-based MBfRs, respectively) and batch tests, indicating nitrate bio-reduction was driven by propane/butane. The consumption rates of nitrate and propane/butane dramatically decreased under anaerobic conditions, but recovered after resupplying limited oxygen, suggesting oxygen was an essential triggering factor for propane/butane-based nitrate reduction. High-throughput sequencing targeting 16S rRNA, bmoX and narG genes indicated Mycobacterium/Rhodococcus/Thauera were the potential microorganisms oxidizing propane/butane, while various denitrifiers (e.g. Dechloromonas, Denitratisoma, Zoogloea, Acidovorax, Variovorax, Pseudogulbenkiania and Rhodanobacter) might perform nitrate reduction in the biofilms. Our findings provide evidence to link SCGA oxidation with nitrate reduction under oxygen-limiting conditions and may ultimately facilitate the design of cost-effective techniques for ex-situ groundwater remediation using natural gas.
硝酸盐污染在水环境中普遍存在，对人类健康构成严重威胁。此前有研究提出甲烷是一种很有前途的电子供体，可用于去除受污染水中的硝酸盐。与纯甲烷相比，天然气不仅含有甲烷，还含有其他短链气态烷烃（SCGAs），价格更低廉，来源更广泛，是去除氧化污染物的更有吸引力的电子源。然而，目前尚不清楚这些 SCGAs 是否可作为硝酸盐还原的电子供体。在这里，我们分别使用丙烷和丁烷为电子供体运行了两个实验室规模的膜生物膜反应器（MBfRs），在缺氧条件下进行实验，以测试微生物硝酸盐还原的可行性。长期运行结果表明，使用丙烷/丁烷作为电子供体时，硝酸盐的去除速率可稳定在 40-50mgN/L/d 左右。在没有丙烷/丁烷的情况下，无论是在长期运行（分别为 2-10mgN/L/d 和 4-9mgN/L/d）还是批处理实验中，硝酸盐去除速率都显著降低，这表明硝酸盐的生物还原是由丙烷/丁烷驱动的。在厌氧条件下，硝酸盐和丙烷/丁烷的消耗速率显著下降，但在重新供应有限氧气后恢复，这表明氧气是丙烷/丁烷还原硝酸盐的必要触发因素。针对 16S rRNA、bmoX 和 narG 基因的高通量测序结果表明，Mycobacterium/Rhodococcus/Thauera 可能是氧化丙烷/丁烷的潜在微生物，而各种反硝化菌（如 Dechloromonas、Denitratisoma、Zoogloea、Acidovorax、Variovorax、Pseudogulbenkiania 和 Rhodanobacter）可能在生物膜中进行硝酸盐还原。本研究结果为在缺氧条件下将 SCGA 氧化与硝酸盐还原联系起来提供了证据，最终可能有助于设计使用天然气进行原位地下水修复的经济有效的技术。
