Beijing Key Laboratory for Source Control Technology of Water Pollution, Engineering Research Center for Water Pollution Source Control and Eco-remediation, College of Environmental Science and Engineering, Beijing Forestry University, 35 Tsinghua East Road, Beijing 100083, China; Department of Microbiology, University of Massachusetts Amherst, Morrill IV N Science Center, Amherst, MA 01003, USA.
Beijing Key Laboratory for Source Control Technology of Water Pollution, Engineering Research Center for Water Pollution Source Control and Eco-remediation, College of Environmental Science and Engineering, Beijing Forestry University, 35 Tsinghua East Road, Beijing 100083, China.
Water Res. 2016 Dec 1;106:71-78. doi: 10.1016/j.watres.2016.09.044. Epub 2016 Sep 23.
A considerable amount of leachate with high fulvic acid (FA) content is generated during the municipal solid waste (MSW) incineration process. This incineration leachate is usually processed by downstream bio-methanogenic treatment. However, few studies have examined the impact that these compounds have on methanogenesis and how they are degraded and transformed during the treatment process. In this study, a laboratory-scale expanded granular sludge bed (EGSB) reactor was operated with MSW incineration leachate containing various concentrations of FA (1500 mg/L to 8000 mg/L) provided as the influent. We found that FA degradation rates decreased from 86% to 72% when FA concentrations in the reactor were increased, and that molecular size, level of humification and aromatization of the residual FA macromolecules all increased after bio-methanogenic treatment. Increasing FA influent concentrations also inhibited growth of hydrogenotrophic methanogens from the genus Methanobacterium and syntrophic bacteria from the genus Syntrophomonas, which resulted in a decrease in methane production and a concomitant increase in CO content in the biogas. Sequences most similar to species from the genus Anaerolinea went up as FA concentrations increased. Bacteria from this genus are capable of extracellular electron transfer and may be using FA as an electron acceptor for growth or as a shuttle for syntrophic exchange with other microorganisms in the reactor. In order to determine whether FA could serve as an electron shuttle to promote syntrophy in an anaerobic digester, co-cultures of Geobacter metallireducens and G. sulfurreducens were grown in the presence of FA from raw leachate or from residual bioreactor effluent. While raw FA stimulated electron transfer between these two bacteria, residual FA did not have any electron shuttling abilities, indicating that FA underwent a significant transformation during the bio-methanogenic treatment process. These results are significant and should be taken into consideration when optimizing anaerobic bioreactors used to treat MSW incineration leachate high in FA content.
在城市固体废物（MSW）焚烧过程中会产生大量含有高腐殖酸（FA）的渗滤液。这种焚烧渗滤液通常通过下游生物甲烷化处理进行处理。然而，很少有研究考察这些化合物对甲烷生成的影响，以及它们在处理过程中是如何降解和转化的。在这项研究中，使用含有不同浓度 FA（1500mg/L 至 8000mg/L）的城市固体废物焚烧渗滤液作为进水，在实验室规模的膨胀颗粒污泥床（EGSB）反应器中进行了操作。我们发现，当反应器中 FA 浓度增加时，FA 的降解率从 86%下降到 72%，并且生物甲烷化处理后，剩余 FA 大分子的分子大小、腐殖化程度和芳构化程度都增加了。增加 FA 进水浓度还抑制了产甲烷菌属 Methanobacterium 和产氢营养型细菌属 Syntrophomonas 的生长，导致甲烷产量减少，沼气中 CO 含量增加。随着 FA 浓度的增加，与 Anaerolinea 属的相似序列也增加了。该属的细菌能够进行细胞外电子转移，可能将 FA 用作生长的电子受体，或作为与反应器中其他微生物进行共代谢交换的穿梭体。为了确定 FA 是否可以作为电子穿梭体来促进厌氧消化器中的共代谢，在存在来自原始渗滤液或剩余生物反应器流出物的 FA 的情况下，培养 Geobacter metallireducens 和 G. sulfurreducens 的共培养物。虽然原始 FA 刺激了这两种细菌之间的电子转移，但残留的 FA 没有任何电子穿梭能力，这表明 FA 在生物甲烷化处理过程中发生了显著的转化。这些结果意义重大，在优化用于处理高 FA 含量的城市固体废物焚烧渗滤液的厌氧生物反应器时应予以考虑。
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