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one for future needs. The existing system is designed for an AWW flow of 1.1 MGD and <br /> a PHWW flow of 3.0 MGD. The existing UV system was designed based on the <br /> following wastewater characteristics. <br /> TSS 30 mg/L <br /> BOD 25 mg/L <br /> UV Transmittal @ 253.7 nm, 65% 50% <br /> Effluent Standard 200/100 ML <br /> For both Design Option No. 1 and No. 2, the existing UV disinfection system would need <br /> upgrades to meet disinfection requirements. <br /> 3.2.10. Electrical/Controls <br /> The current controls system at the Elk River WWTF does not include a central control <br /> system to operate the entire facility. Each treatment unit has its own control system that is <br /> not tied into the control systems of the other treatment units. The existing controls system <br /> is in fine working conditions, but it is not user friendly. Upgrades to the control system <br /> would be beneficial for Design Options No. 1 and No. 2. <br /> 3.3 Biosolids Treatment Process <br /> Biosolids produced during the treatment process are collected in the final and primary clarifiers. <br /> From the final clarifiers the biosolids are transferred by gravity to the primary clarifiers for <br /> thickening. The biosolids are wasted from the primary clarifiers using progressive cavity pumps <br /> with a capacity of 100 gpm. The biosolids treatment process includes one primary and one <br /> secondary anaerobic digester and a biosolids storage tank. The capacity of the existing processes <br /> is discussed below. <br /> 3.3.1. Anaerobic Digestion <br /> The existing anaerobic digestion system includes one completely mixed primary digester <br /> and a secondary digester which is used for biosolids and gas holding. Sizes and capacities <br /> of the digesters are present in Table 3.1. <br /> City of Elk River—T12.104758 Page 12 <br /> Wastewater Treatment Facility Plan Prepared by Bolton&Menk,Inc. <br />