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In comparison, experimental results showed that both solution pH and temperature were significant for defining soluble Mn2+ removal using the MnOx(s)-coated media process; further, the impacts of pH on soluble Mn2+ removal were magnified under low temperature (<10 °C) conditions. Information presented in Table 2 shows the percentage of finished water soluble Mn2+ concentration values that exceeded the recommended Newport News Water Authority goal of 0.015 mg/L when sorted by pH and temperature for the full-scale Harwood's Mill plant data. As shown in Table 2, the percentage of finished water soluble Mn2+ concentration values exceeding the goal generally decreased as the solution temperature increased. Likewise, the percentage of finished water soluble Mn2+ concentration values exceeding the goal of 0.015 mg/L decreased as the pH increased within each temperature range. Finally, results presented in Table 2 also demonstrate that an increase in solution pH may at least partially mitigate the negative effects of low water temperature on Mn removal using MnOx(s)-coated filter media treatment systems.

Table 2

Percentage of finished water soluble Mn concentration values exceeding the target of 0.015 mg/L as a function of water temperature and solution pH (data analyzed from Newport News Water Authority full-scale water plant operations)

 Solution pH value
Temperature5.7–6.06.0–6.36.3–6.6> 6.6
<5 °C 100 60 80 66 
5–10 °C 65 54 61 56 
10–15 °C 45 30 19 
15–20 °C 25 10 
20–25 °C 11 
>25 °C 
 Solution pH value
Temperature5.7–6.06.0–6.36.3–6.6> 6.6
<5 °C 100 60 80 66 
5–10 °C 65 54 61 56 
10–15 °C 45 30 19 
15–20 °C 25 10 
20–25 °C 11 
>25 °C 

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