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EXECUTIVE SUMMARY <br />The City of Lino Lakes completed a Water Treatment Plant Feasibility Study in 2020 that recommended <br />conducting a water treatment pilot study to test the effectiveness of biological filtration to remove <br />manganese from the City's drinking water. The Minnesota Department of Health (MDH) considers biological <br />filtration to be an efficient and effective treatment method remove a wide variety of contaminants including <br />manganese, ammonia, and iron. <br />WSB's pilot trailer was mobilized to Well House No. 6 towards the end of September 2021 to start a <br />biological filtration pilot study that ended on November 26, 2021. WSB's pilot skid tested two types of filter <br />media to identify the best media type to remove manganese biologically. Although both media types had <br />similar removal performance, gravity filters with silica sand and anthracite filter media are recommended <br />for the proposed water treatment plant since the silica sand filter had a lower rate of headloss than the <br />greensand filter and silica sand media is less expensive. The silica sand filter column also showed faster <br />performance recovery in the backwash and shutdown recovery tests. The silica sand filter produced treated <br />water with an average iron concentration of 0.02 mg/L, an average manganese concentration of 0.040 <br />mg/L, and an average ammonia concentration of 0.02 mg/L, all of which are below the target treatment <br />goals set for this pilot study. In addition to achieving excellent removal performance, the silica sand filter <br />column achieved filter run times longer than one week before filter backwashing was required, which is <br />exceptional for water filtration. <br />Implementing biological filtration at the proposed water treatment plant will eliminate the need to <br />prechlorinate the water and to feed sodium or potassium permanganate to oxidize iron, ammonia, and <br />manganese. These chemicals are required in conventional filtration facilities and are costly to feed. The <br />reduction in chemical usage is projected to generate approximately $950,000 in operational savings over <br />the next 20 years when compared to a conventional filtration facility in Lino Lakes. In addition to generating <br />operational savings, utilizing fewer chemicals produces less processed and more sustainable water. <br />Based on the treatment results obtained in this pilot study and the projected operational savings, it is <br />recommended to design and construct a gravity filtration water treatment plant that utilizes biological <br />filtration to remove manganese in Lino Lakes. Data collected in this pilot study will aid in the design of the <br />future facility. <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 1 <br />