Hydrogenotrophic denitrification in a packed bed reactor: Effects of hydrogen-to-water flow rate ratio

Hydrogen dissolution and hydrogenotrophic denitrification performance were investigated in a lab-scale packed bed reactor (PBR) by varying the hydrogen flow rate and hydraulic retention time (HRT). The denitrification performance was enhanced by increasing the hydrogen flow rate and HRT as a result of high dissolved hydrogen concentration (0.39 mg/L) and utilization efficiencies (79%). In this study, the hydrogen-to-water flow rate ratio (Qg/Qw) was found to be a new operating factor representing the two parameters of hydrogen flow rate and HRT. Hydrogen dissolution and denitrification efficiency were nonlinearly and linearly correlated with the Qg/Qw, respectively. Based on its excellent linear correlation with denitrification efficiency, Qg/Qw should be greater than 2.3 to meet the WHO’s guideline of nitrate nitrogen for drinking water. This study demonstrates that Qg/Qw is a simple and robust factor to optimize hydrogen-sparged bioreactors for hydrogenotrophic denitrification.