Both contactors performed well in terms of lowering the treated Mn concentration to values at or below 0.02 mg/L; only a few observed values exceeded 0.02 mg/L, and even in those instances, the EPA secondary MCL of 0.05 mg/L was achieved. The contactor performance data for Mn removal are summarized in Tables 1 and 2. Both contactor media configurations yielded average effluent Mn concentrations that were below the 0.015 mg/L threshold to protect against aesthetic concerns (Brandhuber et al. 2013).

Table 1

Summary of contactor performance data for manganese removal

Media typeInfluent Mn (mg/L)
Minimum–Maximum (average)
Effluent Mn (mg/L)
Minimum–Maximum (average)
Average percent reduction in Mn
1.6 mm ES ceramic 0.007–0.096 (0.044) 0.004–0.040 (0.010) 61 
2.0 mm ES anthracite coal 0.009–0.081 (0.037) 0.004–0.040 (0.014) 55 
Media typeInfluent Mn (mg/L)
Minimum–Maximum (average)
Effluent Mn (mg/L)
Minimum–Maximum (average)
Average percent reduction in Mn
1.6 mm ES ceramic 0.007–0.096 (0.044) 0.004–0.040 (0.010) 61 
2.0 mm ES anthracite coal 0.009–0.081 (0.037) 0.004–0.040 (0.014) 55 
Table 2

Impacts of hydraulic loading rate on Mn removal across pilot-scale contactors

Hydraulic loading rate, m/hr (gpm/ft2)Mn removal for 1.6 mm ES ceramic media (%)Mn removal for 2.0 mm ES anthracite coal media (%)
29.4 (12) 61 60 
37.8 (15) 57 48 
Hydraulic loading rate, m/hr (gpm/ft2)Mn removal for 1.6 mm ES ceramic media (%)Mn removal for 2.0 mm ES anthracite coal media (%)
29.4 (12) 61 60 
37.8 (15) 57 48 

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