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Data from the laboratory-scale column studies (shown in Figures 7 and 8) show pH-sorted soluble Mn2+ concentrations as a function of temperature for the 10-cm media depth and the 25-cm media depth, respectively. As was seen in the full-scale Harwood's Mill data evaluation, a decrease in water temperature yielded a decreased ability of the MnOx(s)-coated media to remove soluble Mn2+ at either media depth. In general, as both the temperature and pH decreased, the soluble Mn2+ concentration in the column increased. For example, soluble Mn2+ concentrations at 5 °C were higher for data in the pH range of 6.0–6.5 than data in the pH range of 6.5–7.0. It should be noted that soluble Mn2+ concentrations were below the recommended target of 0.015 mg/L at temperatures below 10 °C for pH conditions greater than 7.5. Data presented in Table 1 show mean soluble Mn2+ concentration as a function of pH under low water temperature conditions (4–7 °C) for the laboratory-scale data. As shown in Table 1, soluble Mn2+ concentration decreased with an increase in solution pH.
Table 1

Mean soluble Mn concentration as a function of pH for temperatures between 4 and 7 °C

 Soluble Mn concentration (μg/L)
pH range10-cm media depth25-cm media depth
<6.0 141 126 
6.0–6.5 67 63 
6.5–7.0 53 39 
7.0–7.5 38 25 
>7.5 
 Soluble Mn concentration (μg/L)
pH range10-cm media depth25-cm media depth
<6.0 141 126 
6.0–6.5 67 63 
6.5–7.0 53 39 
7.0–7.5 38 25 
>7.5 
Figure 7

pH sorted laboratory-scale filter effluent soluble Mn concentration as a function of solution temperature for a 10-cm media depth.

Figure 7

pH sorted laboratory-scale filter effluent soluble Mn concentration as a function of solution temperature for a 10-cm media depth.

Figure 8

pH sorted laboratory-scale filter effluent soluble Mn concentration as a function of temperature for a 25-cm media depth.

Figure 8

pH sorted laboratory-scale filter effluent soluble Mn concentration as a function of temperature for a 25-cm media depth.

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