2020 Volume 56 Issue 3 Pages 33-45
Bicarbonate (HCO3- ) can be used as an inorganic carbon source for hydrogen-based denitrification (HD). Since HCO3- is considered to accelerate the NO2- reduction rate, this study is attempted to minimize the hydraulic retention time (HRT) of HD systems using varied amounts of HCO3- : deficient, moderate, and abundant amounts. The results implied that a low NO2- amount was removed at unsuitably short HRTs, resulting in poor HD efficiency despite being supplemented with abundant HCO3- amounts. HCO3- assisted in rapidly acclimatizing the bacteria having nirS gene, causing higher NO2- reduction rate and aided in changing the bacterial communities. Thauera spp. were the most dominant bacteria in abundant HCO3- conditions, achieving high HD efficiency at 8 to 24 h HRT whereas satisfactory efficiency was achieved in the deficient and moderate HCO3- amount-systems through the collaboration of Rhodocyclaceae, Alcaligenaceae, and Xanthomonadaceae as predominant bacteria in the community. A strong correlation between the abundance of nirS gene and Thauera spp. was also found. The findings in this study revealed the importance of using HCO3- for the enrichment of H2-oxidizing denitrifiers containing nirS gene in order to reduce NO2- accumulation to enhance the HD efficiency.
