Biohydrogen production at pH below 3.0: Is it possible?

Autor(es)

Mota, V. T. ^[1] ; Ferraz Junior, A. D. N. ^[2] ; Trably, E. ^[3] ; Zaiat, M. ^[1]

Afiliação do(s) autor(es)

^[1] Univ Sao Paulo, LPB, Dept Hydraul & Sanit Engn, Sao Carlos Sch Engn, Ave Joao Dagnone, 1100, BR-13563120 Sao Carlos, SP - Brazil

^[2] CNPEM, CTBE, Rua Giuseppe Maximo Scolfaro 10000, BR-13083970 Campinas, SP - Brazil

^[3] Univ Montpellier, INRA, LBE, F-11100 Narbonne - France

• Tipo de documento: Artigo Científico
• Fonte: WATER RESEARCH; v. 128, p. 350-361, JAN 1 2018.
• Citações Web of Science: 8

Resumo

Biological hydrogen production was investigated in continuous acidogenic reactors fed with sucrose at 30 degrees 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 L(-1)d(-1) OLR. Hydrogen production occurred throughout the experimental period with an average effluent pH of only 2.8. The FB, UG and OF-1 reactors presented volumetric hydrogen production rates (VHPR) of 95 +/- 69, 45 +/- 37 and 54 32 mLH(2) L(-1)h(-1), respectively; and H-2 yields (HY) of 1.5 +/- 0.8, 0.8 +/- 0.6 and 1.2 +/- 0.7 molH(2) mol(-1) sucroseconsumed, respectively. The OF-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-2 production, a flocculent UASB was applied in the second experimental phase. In this phase, the HRT of the acidogenic reactor, which was named OF-2, was raised to 4.6 h, resulting in an OLR of 25 gCOD L(-1)d(-1). The VHPR and the HY increased considerably to 175 +/- 44 mLH(2) L(-1)h(-1) and 3.4 +/- 0.7 molH(2) mol(-1) sucros(consumed), 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-2 production by dark fermentation at pH less than 4.0, the OF-2 reactor presented stable, long-term H-2 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-2 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. (C) 2017 Elsevier Ltd. All rights reserved. (AU)

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