Removal of nitrate from groundwater using a hydrogen-based membrane biofilm reactor: The effects of hydrogen pressure and hydraulic retention time

Abstract

The membrane biofilm reactor (MBfR) is a novel system that uses membranes to supply dissolved gas directly to a biofilm growing on the membrane surface. In this study, hydrogen-based MBfR was used to remove nitrate from groundwater. The continuous flow MBfR reactor was operated under varying hydrogen (H2) pressures and hydraulic retention times (HRT) at constant nitrate concentration of 10 mg L -1 over 81 days with nitrate containing simulated groundwater. The study was composed two parts. In the first part of the study, the effect of H2 pressure on nitrate removal was investigated. The results showed that nitrate reduction rate improved as H2 pressure was increased from 2 to 5 psi, and over 98% of total nitrogen removal rate was achieved. In the second part of study, effect of HRT on nitrate removal was investigated under 5 psi H2 pressure. Our results showed stable nitrate removals under varying HRTs and decreasing HRT from 12 h to 1 h did not adversely affect the reactor performance, however, 0.5 HRT adversely affected the nitrate removal performance. The maximum nitrate removal flux of 3.01 g NO3 (0,659 g NO3) was reached. This research showed that H2 based MBfR is effective for removing nitrate from the contaminated groundwater.