Hydrogenogenic CO Conversion in a Moderately Thermophilic (55 °C) Sulfate‐Fed Gas Lift Reactor: Competition for CO‐Derived H2

Thermophilic (55 °C) sulfate reduction in a gas lift reactor fed with CO gas as the sole electron donor was investigated. The reactor was inoculated with mesophilic granular sludge with a high activity of CO conversion to hydrogen and carbon dioxide at 55 °C. Strong competition for H2 was observed between methanogens and sulfate reducers, while the homoacetogens present consumed only small amounts of H2. The methanogens appeared to be more sensitive to pH and temperature shocks imposed to the reactor, but could not be completely eliminated. The fast growth rates of the methanogens (generation time of 4.5 h) enabled them to recover fast from shocks, and they rapidly consumed more than 90% of the CO-derived H2. Nevertheless, steep increases in sulfide production in periods with low methane production suggests that once methanogenesis is eliminated, sulfate reduction with CO-rich gas as electron donor has great potential for thermophilic biodesulfurization