Biohydrogen production in continuous-flow reactor using mixed microbial culture.
The goal of the proposed project was to develop an anaerobic fermentation process that converts negative-value organic wastes into hydrogen-rich gas in a continuous-flow reactor under different operating conditions, such as hydraulic retention time (HRT), heat treatment, pH, and substrates. A series of batch tests were also conducted in parallel to the continuous study to evaluate the hydrogen conversion efficiency of two different organic substrates, namely sucrose and starch. A heat shock (at 90 degrees C for 15 minutes) was applied to the sludge in an external heating chamber known as a sludge activation chamber, as a method to impose a selection pressure to eliminate non-spore-forming, hydrogen-consuming bacteria and to activate spore germination. The experimental results showed that the heat activation of biomass enhanced hydrogen production by selecting for hydrogen-producing, spore-forming bacteria. The batch feeding at a shorter HRT of 20 hours (or higher organic loading rate) favored hydrogen production, whereas, at a longer HRT of 30 hours, methane was detected in the gas phase. The major organic acids of hydrogen fermentation were acetate, butyrate, and propionate. Up to 23.1% of influent chemical oxygen demand was consumed in biomass synthesis. Batch tests showed that the hydrogen-production potential of starch was lower than sucrose, and better conversion efficiency from starch was obtained at a lower pH of 4.5. However, addition of sucrose to starch improved the overall hydrogen-production potential and hydrogen-production rate. This study showed that sustainable biohydrogen production from carbohydrate-rich substrates is possible through heat activation of settled sludge.
Khanal
Samir Kumar
SK
Department of Civil, Construction and Environmental Engineering, Iowa State University, Ames 50011-3232, USA.
Chen
Wen-Hsing
WH
Li
Ling
L
Sung
Shihwu
S
D001421:Bacteria, Anaerobic / Q000378:metabolism*; D018533:Biomass; D019149:Bioreactors; D005285:Fermentation; D006358:Hot Temperature; D006859:Hydrogen / Q000032:analysis / Q000378:metabolism*; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D008697:Methane / Q000032:analysis; D012722:Sewage / Q000737:chemistry / Q000382:microbiology; D013171:Spores, Bacterial; D013213:Starch / Q000378:metabolism*; D013395:Sucrose / Q000378:metabolism*
D012722:Sewage; D013395:Sucrose; D006859:Hydrogen; D013213:Starch; D008697:Methane