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Maximum hydraulic and organic loading capacity of each trickling filter is 1.43 MGD and <br /> 3,308 lbs CBOD5/day, respectively. When the filters are run in parallel the total hydraulic <br /> and organic loading rates are 2.86 MGD and 6,616 lbs/day, respectively. <br /> 3.2.6. Aeration Basin <br /> The existing aeration basin is 40 feet by 20 feet with a side water depth of 12 feet. The <br /> tank was built in 1994 with an adjacent blower building and was intended to be used as a <br /> future aeration tank. However, aeration diffusers and blowers were never installed and the <br /> tank has never been put into service. <br /> 3.2.7. Final Clarifiers <br /> From the trickling filters wastewater flows to the final clarifier splitter structure where <br /> flow is evenly split to three final clarifiers. The existing clarifiers are 50 feet in diameter <br /> with a side water depth of 16 feet. Using the Ten States Standard of 900 gpd/ft2 at Peak <br /> Hourly Flow, maximum capacity of each clarifier is 1.76 MGD (PHWW). The combined <br /> total PHWW flow capacity of all three final clarifiers is 5.28 MGD. <br /> The existing facility is 0.40 MGD short in capacity for Design Option No. 1 and 1.99 <br /> MGD short in capacity for Design Option No. 2. <br /> 3.2.8. Filters <br /> After final clarification, wastewater flows to the gravity sand filters. The existing facility <br /> has six (6) gravity sand filters with a total design flow of 7.0 MGD. Each filter is 12 feet <br /> by 20 feet with a surface area of 240 square feet. Each filter has 10 inches of silica sand <br /> filter media placed directly over the underdrains. <br /> The filtration system has two low pressure air wash blowers. Each blower has a 3.0 HP <br /> motor with a capacity of 300 scfin at 3.0 psi. <br /> 3.2.9. Disinfection <br /> Following the filters wastewater flows to the Disinfection Building for final treatment. <br /> The facility uses ultraviolet (UV) light for effluent wastewater disinfection. The UV <br /> building has two channels, one equipped with UV equipment for current treatment and <br /> City of Elk River—T12.104758 Page 11 <br /> Wastewater Treatment Facility Plan Prepared by Bolton&Menk,Inc. <br />