LPB, Department of Hydraulics and Sanitary Engineering, São Carlos School of Engineering, University of São Paulo (USP), Avenida João Dagnone, 1100, São Carlos, SP, 13563-120, Brazil.
CTBE, CNPEM, Rua Giuseppe Máximo Scolfaro 10000, Campinas, SP, 13083-970, Brazil.
Water Res. 2018 Jan 1;128:350-361. doi: 10.1016/j.watres.2017.10.060. Epub 2017 Oct 30.
Biological hydrogen production was investigated in continuous acidogenic reactors fed with sucrose at 30 °C without pH control. In the first experimental phase, three reactors were compared: a structured fixed-bed (FB), a granular UASB (UG) and a flocculent UASB (UF-1). They were run at 3.3 h HRT and 33 gCOD Ld OLR. Hydrogen production occurred throughout the experimental period with an average effluent pH of only 2.8. The FB, UG and UF-1 reactors presented volumetric hydrogen production rates (VHPR) of 95 ± 69, 45 ± 37 and 54 ± 32 mLH Lh, respectively; and H yields (HY) of 1.5 ± 0.8, 0.8 ± 0.6 and 1.2 ± 0.7 molH mol sucrose, respectively. The UF-1 reactor showed intermediate VHPR and HY, but no declining trend, contrary to what was observed in the FB reactor. Thus, aiming at continuous and long-term H production, a flocculent UASB was applied in the second experimental phase. In this phase, the HRT of the acidogenic reactor, which was named UF-2, was raised to 4.6 h, resulting in an OLR of 25 gCOD Ld. The VHPR and the HY increased considerably to 175 ± 44 mLH Lh and 3.4 ± 0.7 molH mol sucrose, respectively. These improvements were accompanied by greater sucrose removal, higher suspended biomass concentration, less production of lactate and more of acetate, and high ethanol concentration. Contradicting the current published literature data that reports strong inhibition of H production by dark fermentation at pH less than 4.0, the UF-2 reactor presented stable, long-term H production with satisfactory yields at pH 2.7 on average. 16 S rDNA sequencing revealed that two sequences assigned as Ethanoligenens and Clostridium accounted for over 70% of the microbiota in all the reactors. The non-necessity of adding alkalizing agents and the successful H production under very acid conditions, demonstrated in this study, open a new field of investigation in biological hydrogen production by dark fermentation towards a more sustainable and feasible technology.
在 30°C 下，连续酸化反应器中以蔗糖为底物，不进行 pH 控制，研究了生物制氢。在第一实验阶段，比较了三种反应器：结构固定床（FB）、颗粒 UASB（UG）和絮状 UASB（UF-1）。它们在 3.3 h 的 HRT 和 33 gCOD Ld 的 OLR 下运行。整个实验期间均有氢气产生，平均出水 pH 仅为 2.8。FB、UG 和 UF-1 反应器的体积产氢率（VHPR）分别为 95±69、45±37 和 54±32 mLH Lh；氢气产率（HY）分别为 1.5±0.8、0.8±0.6 和 1.2±0.7 molH mol 蔗糖。UF-1 反应器表现出中等的 VHPR 和 HY，但没有像 FB 反应器那样出现下降趋势。因此，为了实现连续和长期的氢气生产，在第二实验阶段应用了絮状 UASB。在该阶段，酸化反应器的 HRT 提高到 4.6 h，OLR 提高到 25 gCOD Ld，将该反应器命名为 UF-2。VHPR 和 HY 大幅提高至 175±44 mLH Lh 和 3.4±0.7 molH mol 蔗糖。这些改进伴随着更高的蔗糖去除率、更高的悬浮生物量浓度、更少的乳酸产生和更多的乙酸产生，以及高乙醇浓度。与当前发表的文献数据相反，该数据报告了在 pH 值小于 4.0 的黑暗发酵中，氢气的产生受到强烈抑制，UF-2 反应器在平均 pH 值为 2.7 的情况下稳定、长期地生产氢气，产率令人满意。16S rDNA 测序表明，在所有反应器中，两个序列被分配为乙醇杆菌属和梭菌属，占微生物群的比例超过 70%。本研究表明，在非常酸性的条件下不需要添加碱化剂，并且可以成功地生产氢气，为黑暗发酵生物制氢开辟了一个新的研究领域，朝着更可持续和可行的技术方向发展。
