Investigating the effects of operational parameters on photofermentation in batch and semi-batch reactors and the applications of photofermentation in multi-stage energy systems

Akman, Melih Can
The aim of this thesis study was to investigate the effects of operational parameters on photofermentation in batch and semi-batch reactors, and the application of photofermentation in multi-stage energy systems. Firstly, three operational conditions of the substrate concentration, Volatile Suspended Solids (VSS) concentration and the light intensity leading to the maximization of hydrogen production in a single stage were optimized. The highest hydrogen production rate (HPR) of 1.04 mmol H2/L.h was achieved at the optimum values of 35.35 mM HAc initial substrate concentration, 0.27 g VSS/L initial biomass (Rhodobacter capsulatus) concentration and 3955 lux (263.6 W/m2) light intensity. The highest HPR obtained in batch reactors, as second-stages of a two-stage dark fermentation and photofermentation system, was 0.48±0.08 mmol H2/L.h and hydrogen yield was 1.61±0.24 mol H2/mol acetate. The highest HPR and hydrogen yield were observed as 0.10±0.005 mmol H2/L.h and 0.95±0.03 mol H2/mol acetate in batch photofermentation reactors, as third-stages of a three-stage system composed of dark fermentation, methanogenesis and photofermentation processes in sequence. Finally, the HRT value leading to the highest hydrogen production was observed as 4 days in semi-batch photofermentation reactors in a three-stage system. The results of this thesis study are believed to be beneficial in photobioreactor designs and operational conditions for photofermentative hydrogen production with greater rates. Both the photofermentative hydrogen production yields and total energy yields obtained in three-stage system, which is not studied so far in literature, provide a preliminary knowledge for future three-stage systems and comparison for two-stage systems frequently encountered in literature.


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The aim of this master thesis study was to investigate the dark fermentative hydrogen production in batch and sequencing batch reactors (SBRs), and to investigate operational conditions leading to its maximization. Batch reactor studies were conducted to determine the initial operational conditions for the subsequent SBR operation. Two batch reactor sets, conducted with either sucrose or molasses as substrate, were operated to investigate the effect of initial pH, chemical oxygen demand (COD) and volatile s...
Heat transfer enhancement in turbulent upward flows of liquid-solid suspensions through vertical annuli
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The problem studied in this thesis, is the classification of the small-scale aircraft targets by using a natural resonance based electromagnetic feature extraction technique. The aircraft targets are modeled by perfectly conducting, thin wire structures. The electromagnetic back-scattered data used in the classification process, are numerically generated for five aircraft models. A contemporary signal processing tool, the Wigner-Ville distribution is employed in this study in addition to using the principal...
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The detection of an energetic molecule TNT is an important issue especially in military applications and as a result many of the studies focused on this subject in the literature. In this study, except from the literature, the possible interactions between TNT and polycyclic aromatic chiral compound (R)-Hexahelicene were examined theoretically in terms of non-covalent pi-pi interactions, theoretically. It was observed that (R)-Hexahelicene had such interactions with TNT via the 2nd and 3rd six-membered ring...
Citation Formats
M. C. Akman, “Investigating the effects of operational parameters on photofermentation in batch and semi-batch reactors and the applications of photofermentation in multi-stage energy systems,” M.S. - Master of Science, Middle East Technical University, 2018.