Microstructure and molecular microbiology of rapidly formed hydrogen‐ and methane‐producing granules in a phase‐separated anaerobic environment

Hydrogen and methane were simultaneously produced in a two‐phase reactor, operated to separate the reactions of hydrogen and methanogen production. Each reactor was inoculated with a seed enriched with different microbial consortia. The first phase was operated with a hydraulic retention time of 7 days and at an organic loading rate of 7.7 g VS L^?1 d^?1 that produced a stable pH of 5.5. This suppressed the growth of methanogens and as a result, the off gas contained up to 27% hydrogen. The second phase was operated with a hydraulic retention time of 12 days and at an organic loading rate of 3.6 g VS L^?1 d^?1. This permitted the growth of hydrogenotrophs and methanogens to produce methane at a concentration of 60%. Examination of the microbial population of the two reactors both microscopically and using PCR, showed an effective separation of hydrogen‐ and methane‐producing microbial communities. The study revealed that the suppression of hydrogentrophs and methanogens can be achieved by adopting rapid method that leads the growth of hydrogen‐ and methane‐producing granules in phase‐separated anaerobic environment.