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5.2 Iron Removal <br />The iron removal results obtained in this pilot study are shown in Figure 5-2. The figure below shows the <br />raw water iron concentration, the effluent iron concentration (Filter 1 and Filter 2), and the effluent target <br />iron concentration. The iron concentration in the water was reduced from an average of 0.05 mg/L to an <br />average of 0.02 mg/L. Both biological filters produced similar effluent iron concentrations throughout the <br />pilot study. The average filter effluent concentration is approximately 93-percent below the EPA SDWS for <br />iron. <br />0.5 <br />0.4 <br />J <br />C <br />0.3 <br />0 <br />m <br />0.2 <br />U <br />C <br />O <br />0.0 <br />09/22/21 <br />09/29/21 10/06/21 10/13/21 10/21 /21 10/28/21 11 /04/21 11 /11 /21 11 /19/21 <br />Date (mm/dd/yy) <br />X Raw Influent ♦ Filter 1 Effluent ❑ Filter 2 Effluent Effluent Target Conc. <br />Figure 5-2. Biological Iron Removal <br />The iron removed by the filters increased during the treatment efficiency phase when compared to the <br />acclimation phase. Although Filter 2 had a better removal performance than Filter 1, the difference in <br />effluent iron concentration between the two filters during the treatment efficiency phase was only 0.01 mg/L. <br />Table 5-2 below summarizes the average iron removed by the filters during both phases of the study. <br />Table 5-2. Iron Removal Efficiency <br />Phase <br />Avg. Iron Removal <br />Filter 1 <br />Filter 2 <br />Acclimation <br />24% <br />32% <br />Treatment Efficiency <br />63% <br />82% <br />5.3 Manganese Removal <br />The manganese removal results obtained in this pilot study are shown in Figure 5-3. The figure below <br />shows the raw water manganese concentration, the effluent manganese concentration (Filter 1 and Filter <br />2), and the effluent target manganese concentration. The manganese concentration in the water was <br />reduced from an average of 0.410 mg/L to an average of 0.040 mg/L in Filter 1 and 0.023 mg/L in Filter 2 <br />during the treatment efficiency phase. Although Filter 2 produced water with lower manganese <br />concentrations, the effluent manganese concentrations from both filters were almost identical towards the <br />end of the study. All effluent manganese concentrations during the treatment efficiency phase were below <br />EPA's SDWS for manganese and the MDH's guidance values of 0.10 mg/L for infants and 0.30 mg/L for <br />children and adults. <br />Water Treatment Pilot Study Report <br />Biological Removal of Ammonia, Iron and Manganese at Well House No. 6 <br />City of Lino Lakes, MN <br />WSB Project No. 0 18601 -000 Page 8 <br />