Study on the Factors Affecting the Start-Up of Iron-Manganese Co-Oxide Filters for Ammonium and Manganese Removal from Groundwater

Abstract

The high concentration of ammonium (NH ₄ ⁺-N) and manganese (Mn ²⁺) in underground water poses a major problem for drinking water treatment plants. Effective catalytic oxidative removal of NH ₄ ⁺-N and Mn ²⁺ by iron-manganese co-oxide film (MeO _x) filters was first developed by our group in a previous study. In this study, several identical pilot-scale filters were employed to optimize the start-up process for simultaneous removal of NH ₄ ⁺-N and Mn ²⁺ from potable water supplies. Experiments were conducted to assess the influence of Mn ²⁺ concentration, Fe ²⁺ concentration, filtration rate and dosing time on the start-up period of the filter. Results demonstrated that the ability of the filter to remove completely 1.5 mg/L NH ₄ ⁺-N could be achieved on the sixth day at the soonest and the removal of Mn ²⁺ could reach 1 mg/L by the 18th day. Filter R3 feeding with 1 mg/L Fe ²⁺, 2 mg/L Mn ²⁺ and 3.5 mg/L MnO ₄ ⁻ during the start-up period exhibited the optimum NH ₄ ⁺-N and Mn ²⁺ removal effect. Short dosing time was not conducive to attaining full NH ₄ ⁺-N removal in filters, especially the activity of NO ₂ ⁻-N conversion to NO ₃ ⁻-N. The compositional analysis and element distribution analysis results demonstrated that there was an abundance of C, O, Mn, Mg, Fe, Ca and Si across the entire area of the surface of the filter media and the elemental distribution was homogeneous, which was different from the biofilter media. Knowledge-guided performance optimization of the active iron-manganese co-oxide could pave the way for its future technological use.