Cultivation of hydrogenotrophic microorganisms and the denitrification characteristics

Abstract:

[Objective] We screened out hydrogenotrophic microorganisms using inorganic carbon sources for high efficiency in denitrification under weak acidic conditions, to investigate the effects of different inorganic carbon sources on the denitrification capacity of the system, and to explore the variation in water quality parameters, microbial community structure, and denitrification cycle in the reactor during long-term cultivation. [Methods] We developed a sequential batch reactor for continuous cultivation of microorganisms by supplying hydrogen, inorganic carbon source, nutrient solution and nitrate in time, and the apparatus have the advantages of low cost, excellent air tightness, and hydrogen utilization rate calculation. [Results] The cultivated microorganisms showed higher efficiency in denitrifying nitrates with the mixture of NaHCO₃ and CO₂ as inorganic carbon sources than that of NaHCO₃ as solo carbon source. Under the conditions of ambient temperature of 20 ℃, pH of 6.3-7.0, and initial nitrate nitrogen dosage of 15 mg-N/L, the highest reaction rate of NO₃^--N was 1.374 mg-N/(L·h) and the highest utilization rate of hydrogen was 43.4%. In addition, the denitrification cycle was 16 h, with no nitrite accumulation detected. The cultivated microorganisms were mainly Acidovorax, accounting for 84.4%. [Conclusion] It is feasible and efficient to use this apparatus and method to cultivate microorganisms. Hydrogenotrophic microorganisms could be screened for denitrification by inorganic carbon source under weak acidic condition. The findings lay a theoretical basis for the bioremediation of groundwater polluted by nitrate and a foundation for the simultaneous denitrification and uranium fixation of hydrogenotrophic microorganisms in acidic environment in the near future.