Investigation of hydrogen-based denitrification performance on nitrite accumulation under various bicarbonate doses

Nitrate-contamination in groundwater sources has been globally taken as a crucial issue due to the effects of nitrate on human health, e.g., methaemoglobinaemia. Various processes have been applied for the treatment of contaminated groundwater with nitrate. Hydrogen-based autotrophic denitrification (hydrogenotrophic denitrification) is an alternative process used for abatement of the nitrate-contamination. Although high efficiency on nitrate removal was achieved by former research, it is unclear whether the growth of true denitrifiers is affected by inorganic carbon in which this is essential to comprehend the principal cause of nitrite accumulation. This study found that inorganic carbon had no impact on the nitrate reduction rate whereas the nitrite reduction rate was improved when a higher amount of inorganic carbon was supplied. Also, using bicarbonate as an inorganic carbon source had a positive effect on the growth and adaptation of true denitrifiers that can reduce the nitrite accumulation in hydrogen-based denitrification system.