Effects of Fe(OH)₃ and MnO₂ Flocs on Iron/Manganese Removal and Fouling in Aerated Submerged Membrane Systems

Many treatment methods are used to remove iron and manganese from water. Aeration and membrane filtration are two of these methods. In this study, Fe²⁺ and Mn²⁺ removal by aeration with different catalysts and instead of simple membrane filtration applied in other studies, the aerated-submerged membrane systems were evaluated separately. When Fe(OH)₃ was applied in the aeration step and complete oxidation of Fe²⁺ was obtained after 27 min, while complete Mn²⁺ oxidation was obtained in 76 min. However, when MnO₂ was applied in the aeration step, complete oxidation of Fe²⁺ and Mn²⁺ was relatively slow (36 and 110 min, respectively). According to the results obtained from the aerated membrane system, Fe²⁺ and Mn²⁺ removal were extended by Fe(OH)₃ via adsorption/surface oxidation. It is clearly shown from the flux, resistance results, scanning electron microscope (SEM) and Fourier transform infrared (FT/IR) spectroscopy observation that manganese oxides were deposited mainly in membrane pores forming membrane fouling by small flocs, while iron oxide particles were deposited on the membrane surface. Although the flux performance of PT PES membrane was higher than HF PP membrane, fouling resistance of HF PP membrane was higher than PT PES.