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4.1.3 <br />4.2 <br />4.2.1 <br />of detention allows for additional chemical reaction time to increase iron oxidation. The <br />potassium permanganate dosage in Train 2 was able to be lowered to about a fifth of that in Train <br />1, as the added chemical reaction time with 30 minutes of detention increases manganese <br />oxidation. <br />Finished Water Quality <br />The SEH pilot water plant was able to treat water from Well No. 3 to levels that meet the EPA <br />secondary standards, as well as MDH's HBV for manganese. In fact, no sample result exceeded <br />the EPA secondary standards, and both treatment trains were able to remove both iron and <br />manganese on average below the method detection limits of 0.011 mg/L and 0.020 mg/L <br />respectively. <br />The finished water quality for Well No. 3 during the pilot study is summarized in Table 4 below. <br />Table 4-Well No. 3 Finished Water Quality <br />Filter <br />Iron <br />1 <br />(mg/L) <br />Manganese (mg/L) <br />Avg. <br />1 C'� <br />Avg. ii - <br />1 <br />nd <br />nd <br />0.040 <br />nd <br />nd <br />0.043 <br />2 <br />nd <br />nd <br />0.020 <br />nd <br />nd <br />nd <br />3 <br />nd <br />nd <br />0.020 <br />nd <br />nd <br />0.048 <br />4 <br />nd <br />nd <br />nd <br />nd <br />nd <br />nd <br />Notes: nd = below method detection limit <br />The use of detention in Train 2 did not provide a significant treatment advantage over Train 1 in <br />removing iron and manganese, although the use of aeration in Train 2 provided slightly better <br />results in the removal of iron. There also wasn't a significant difference in treatment <br />effectiveness between the two filter media types, although Filters 1 and 3 each had at least one <br />spiked result for manganese that approached the secondary standard. <br />Well No. 4 Results <br />Raw Water Quality <br />The pilot study for Well No. 4 was completed between January 20, 2020 and January 21, 2020. <br />Well No. 4 currently pumps approximately 850 gpm directly into the distribution system with <br />polyphosphate, chlorine, and fluoride added in a shared pump house with Well No. 3. Table 5 <br />below summarizes the raw water results collected from Well No. 4 during the pilot study. <br />Table 5 - Well No. 4 Raw Water Quality <br />Iron (mg/L) <br />Manganese (mg/L) <br />Min. <br />Avg. <br />Max. <br />Min. <br />Avg. <br />Max. <br />Min. <br />Avg. <br />Max. <br />0.180 <br />0.240 <br />0.360 <br />0.035 <br />0.392 <br />0.360 <br />7.51 <br />7.61 <br />7.71 <br />Results from the raw water sampling show that Well No. 4 exceeds EPA's secondary standards <br />for iron and manganese, which can cause aesthetic water quality issues related to color, taste, <br />PILOT STUDY REPORT RAMSY 154354 <br />Page 6 <br />