Development of novel Bubble Column Reactor (BCR) for iron removal in groundwater

Abstract

Iron in groundwater mostly in ferrous form with the high concentration is likely the most common water problem. Bubble Column Reactor (BCR) or Airlift Reactor (ALR) is one of the best multiphase contactors that provides many advantages in aeration and oxidation. However, several inadequate points are still required to refin for improving its efficiency. This work aimed to optimize the novel reactor for improving the aeration process and ferrous iron oxidation. Novel Bubble Column Reactor (Novel BCR) that has a cross sectional dimension of 0.4m×0.5m (140L capacity), was developed by inserting the vertical baffle to create a liquid recirculation from a riser to downcomer compartment, and installing horizontal baffles in a riser to increase the bubble retention time and improve the air bubble distribution. Bubble hydrodynamic parameter was studied for well understand the internal mechanism in the reactor. The optimum level of Novel BCR was obtained from the condition that provided overall maximum liquid mass transfer coefficient (KLa) after variation of various parameters. Main influenced factors of Novel BCR performance are the position of recirculation area (Yr), amount of baffle (Nb), settling area on baffle (AS), and baffle angle (α) with respective value: 10cm, 3 baffles, 90cm2, and 50° at 0.45 of optimum downcomer-to-riser ratio. Novel BCR improved the oxygen transfer in terms of KLa coefficient from 50% to 97% compared to conventional BCR and 6% to 28% compared to ALR in the ranges of gas flow rate of 4 - 16 LPM. Moreover, the study of ferrous iron oxidation in this novel reactor was conducted by varying initial concentrations of ferrous iron (5 to 50 mg/L) and gas flow rates (2 to 10 LPM) as a semi-batch reactor. The oxidation is faster at lower initial concentration of ferrous iron and the operation in Novel BCR exhibited greater ferrous oxidation than conventional BCR. In the studied gas flow rates, increasing gas flow rate improved conversion yield of ferrous iron.