Investigation on Bioreactor Operating Parameters for Optimum Microbial Hydrogen Production

As fuel costs continue to increase, novel methods to produce energy are becoming very important. Methods to generate hydrogen from organic material for utilization in fuel cells have been the source of much research over recent decades. One method to generate hydrogen is through microbial treatment of waste streams. The microbial treatment of wastes has great potential due to the mild conditions required to maintain biological systems, and other benefits such as removal of waste during the reaction process. The purpose of this research was to determine conditions in a bioreactor that would lead to the optimum rate of hydrogen production by manipulating process parameters. This was done by studying the affects of pH, temperature, organic loading rate, and hydraulic retention time in batch and continuous flow mixed bacterial culture reactors. The bacterial culture used in these experiments was able to generate the maximum amount of hydrogen from two different substrates in a reactor with a pH 5.2-5.7. The bacterial culture was able to convert substrates with the highest generation rate of hydrogen at 30 oC with a maximum of 0.25±0.01 mg H2/g COD h, while still being able to produce hydrogen at 40 oC with a maximum of 0.09±0.004 mg H2/g COD h. The optimum hydraulic retention time was found to be between 18 and 20 hours. Tests were conducted using loading rates between 55 and 450 mg COD/L and showed the maximum conversion of substrate occurred at 55 mg COD/L. These results indicate that hydrogen generation in a bacterial reactor will not be a sufficient method to generate power for further use, but could be feasible if used in conjunction with other sources of energy production.