Conceptualization, T.H.; methodology, X.X., T.H. and Y.C.; validation, Y.C., R.H., G.W. and K.L.; formal analysis, X.X.; investigation, X.X., K.L. and R.H.; data curation, X.X.; writing—original draft preparation, X.X.; visualization, G.W.; supervision, Y.C.; project administration, R.H. All authors have read and agreed to the published version of the manuscript.

Figure 1. Schematic of the pilot experimental system for the catalytic oxidation of surface water for treatment.

Figure 1. Schematic of the pilot experimental system for the catalytic oxidation of surface water for treatment.

Figure 2. Effectiveness of the oxide film in removing (a) Mn2+ and (b) NH4+-N during continuous operation.

Figure 2. Effectiveness of the oxide film in removing (a) Mn2+ and (b) NH4+-N during continuous operation.

Figure 3. Scanning electron microscopy images of the oxide film. (a) Original oxide film, (b) after 15 days of operation, and (c) after 120 days of operation. The images on the left and right were taken at 100× and 1000× magnification, respectively.

Figure 3. Scanning electron microscopy images of the oxide film. (a) Original oxide film, (b) after 15 days of operation, and (c) after 120 days of operation. The images on the left and right were taken at 100× and 1000× magnification, respectively.

Figure 4. X-ray diffractometry patterns of the filter medium during the operation of the filter column.

Figure 4. X-ray diffractometry patterns of the filter medium during the operation of the filter column.

Figure 5. Fourier-transform infrared spectrometry spectra of the filter medium during the operation of the filter column.

Figure 5. Fourier-transform infrared spectrometry spectra of the filter medium during the operation of the filter column.

Figure 6. Effects of alkalinity on the effectiveness of the oxide film in removing (a) Mn2+ and (b) NH4+-N.

Figure 6. Effects of alkalinity on the effectiveness of the oxide film in removing (a) Mn2+ and (b) NH4+-N.

Figure 7. Precision titration experiment. (a) Relationship between the increase in the concentration in H+ and pH of the raw water, and (b) the relationship between the removal of Mn2+ and the release of H+.

Figure 7. Precision titration experiment. (a) Relationship between the increase in the concentration in H+ and pH of the raw water, and (b) the relationship between the removal of Mn2+ and the release of H+.

Figure 8. Effects of pH on the removal efficiency of Mn2+.

Figure 8. Effects of pH on the removal efficiency of Mn2+.

Table 1. Water-quality parameters of the influent entering the filter column.

Table 1. Water-quality parameters of the influent entering the filter column.

Water Quality IndicationsUnitValue1T℃18–212DOmg·L–14.3–6.93pH-7.04–7.504TurbidityNTU1.17–2.695CODMnmg·L–11.07–1.946TPµg·L–1<157Total dissolved solidsmg·L–140–508Alkalinitymg·L–1(expressed in CaCO3 equivalent)30–409Total aluminumμg·L–1<30

Table 2. Content, specific surface area, pore volume, and pore size of the oxide film on the surface of the filter medium.

Table 2. Content, specific surface area, pore volume, and pore size of the oxide film on the surface of the filter medium.

NoOperation Time (day)Specific Surface Area (m2/g)Pore Volume (cm3/g)Pore Size
(nm)Surface Oxide Content (mg/g)1Initial stage of operation1.150.003813.8612.662151.39 0.004212.3319.4831201.810.004914.0032.43

Table 3. Changes in the main elemental composition of the filter medium containing Fe–Mn composite oxides.

Table 3. Changes in the main elemental composition of the filter medium containing Fe–Mn composite oxides.

O
(%)Al
(%)Si
(%)K
(%)Ca
(%)Mn
(%)Fe
(%)Initial stage of operation54.454.832.160.101.1736.231.06After 20 days of operation49.084.951.170.421.5841.451.35After 100 days of operation42.130.150.9200.6353.582.65