Abstract
Iron oxidation and removal from groundwater is a necessary and costly process in drinking water production. In most cases, iron removal is done via aeration, succeeded by precipitation. Most systems for aeration are based on increasing the interfacial area via injecting air in the system or spraying. Both methods have disadvantages, like clogging and formation of aerosols. In this study, a new vortex-based flow-through reactor consisting of a cylindrical tank with an impeller located at the bottom was studied regarding its aeration and iron oxidation capabilities in groundwater. During the aeration experiments, the flow rate, impeller rotation and aerated volume were varied. A nondimensional constant α was proposed to relate the system’s physical characteristics and its aeration capabilities, expressed in dissolved oxygen and system volumetric mass transfer coefficient (KLa). Three distinct operational regimes were defined: formation, complete and bubble regime. These regimes showed very specific characteristics regarding the air–water interface structure and the area to volume ratio, resulting in different aeration capabilities and iron oxidation efficiency values. The system presented KLa values similar to commercially available aeration systems, especially inside the bubble regime. By using dimensionless coefficients, the presented analysis provided the basis for the design of continuous impeller aeration and oxidation systems of arbitrary size.
Highlights
Aeration is a commonly used and an important step applied in water and wastewater treatment processes [1,2]
We presented a study regarding the performance of a novel impeller-based aeration system providing high aeration capabilities and reduced formation of aerosols in a compact flow-through setup
In order to relate the aeration number Flg [18] with the geometry of the tank, we proposed the nondimensional coefficient α according to Equation (9), α = log10 ( Fl g h· DT −1 )−1, (9)
Summary
Aeration is a commonly used and an important step applied in water and wastewater treatment processes [1,2]. It is a technique in which air and water are brought into close contact, normally with the objective of increasing the dissolved oxygen content in the water body in order to provide, e.g., oxidation of dissolved metals, volatile organic chemicals [3]. Maintenance of biota equilibria in open waters. It can be used, inversely, to decrease the concentration of a specific gas in the liquid phase (in this case, the process is called stripping). Diffusion aerators inject gas under pressure into the liquid phase [4].
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