Lactate wastewater dark fermentation: The effect of temperature and initial pH on biohydrogen production and microbial community

Authors: ZIARA, RAMI - University Of Nebraska; Miller, Daniel; SUBBIAH, JEYAMKONDAN - University Of Nebraska; DVORAK, BRUCE - University Of Nebraska

Submitted to: International Journal of Hydrogen Energy
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/2/2018
Publication Date: 12/6/2018
Citation: Ziara, R.M., Miller, D.N., Subbiah, J., Dvorak, B.I. 2018. Lactate wastewater dark fermentation: The effect of temperature and initial pH on biohydrogen production and microbial community. International Journal of Hydrogen Energy. 44(2):661-673. https://doi.org/10.1016/j.ijhydene.2018.11.045.
DOI: https://doi.org/10.1016/j.ijhydene.2018.11.045

Interpretive Summary: Biohydrogen production using dark fermentation (hydrolysis and acidogenesis) is one of the ways to recover energy from energy-rich food-processing wastewater. Dark fermentation can be affected by the temperature, pH and the microbial community structure. This study investigated the effects of temperature and initial pH on the biohydrogen production and the microbial community from a lactate wastewater using dark fermentation. Biohydrogen production was most at moderate temperatures (35 and 45°C) and neutral pH (6.5, 7.5 and 8.5). The highest hydrogen yield (0.85 mol H2/ mol lactate consumed) was achieved at 45°C and initial pH 8.5. A reduction in chemical oxygen demand (COD) was achieved by fermenting the lactate wastewater at 35°C and ranged between 21 and 30% with the maximum reduction at pH 8.5. At 45°C, the COD reduction ranged between 12 and 21%, with the maximum at pH 7.5. At 35°C, the lactic acid degradation ranged between 54 and 95%, while at 45°C, it ranged between 77 and 99.8%. Ribosomal sequencing revealed that at 35°C, bacteria from the Clostridium genera were the most abundant at the end of the fermentation in the reactors that produced hydrogen, while at 45°C Sporanaerobacter, Clostridium and Pseudomonas were the most abundant.

Technical Abstract: Biohydrogen production using dark fermentation (hydrolysis and acidogenesis) is one of the ways to recover energy from energy-rich food-processing wastewater. Dark fermentation can be affected by the temperature, pH and the microbial community structure. This study investigated the effects of temperature and initial pH on the biohydrogen production and the microbial community from a lactate wastewater using dark fermentation. Biohydrogen production was successful only in the mesophilic temperature range (35 and 45°C) and initial pH 6.5, 7.5 and 8.5. The highest hydrogen yield (0.85 mol H2/ mol lactate consumed) was achieved at 45°C and initial pH 8.5. The COD reduction achieved by fermenting the lactate wastewater at 35°C ranged between 21 and 30% with the maximum COD reduction at pH 8.5, and at 45°C, the COD reduction ranged between 12 and 21%, with the maximum at pH 7.5. At 35°C, the lactate degradation ranged between 54 and 95%, while at 45°C, it ranged between 77 and 99.8%. 16s rRNA sequencing revealed that at 35°C, bacteria from the Clostridium genera were the most abundant at the end of the fermentation in the reactors that produced hydrogen, while at 45°C Sporanaerobacter, Clostridium and Pseudomonas were the most abundant.