8.1. SR 03-18-2013 - Laserfiche WebLink

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4.3.1. Pump to Great River Energy (GRE) This option would consist of pumping untreated biosolids to GRE for processing. In return, GRE would require the Elk River WWTF to take clarifier water from GRE for treatment. Clarifier flows from GRE would be approximately 150,000 gpd which is fairly insignificant at the future design flows for the Elk River WWTF. Since GRE would accept untreated biosolids, the Elk River WWTF could abandon the existing biosolids treatment process and utilize the existing infrastructure to support pumping of biosolids to GRE. This would include addition of an aeration system in the existing digester and sludge storage tank so they could be used as aerated storage for biosolids that are to be pumped to GRE. Pumping and piping modifications would also be required to pump biosolids to GRE. Design of this system would be done to accommodate biosolids production for Design Option No. 1 and No. 2. A biosolids process flow diagram for this option is provided in Figure 4.4. 4.3.2. Expansion of Existing Anaerobic Digestion System Based on the existing system capacity, expansion of the existing aerobic treatment system would be required to meet future needs. The maximum capacity of the existing anaerobic digesters is 4,470 lbs of dry sludge/day which presents a capacity deficit of 8,930 lb/day and 12,680 lb/day for design Options No. 1 and No. 2, respectively. To meet the future demands, design of the digesters was done using the maximum loading rate of 80 lbs VSS/l'000ft3/day per Ten States Standards. Based on this design standard Design Option No. 1 would require two 55 foot diameter digesters with a side water depth of 20 feet while Design Option No. 2 would require three digesters with the same dimensions. City of Elk River—T12.104758 Page 25 Wastewater Treatment Facility Plan Prepared by Bolton&Menk,Inc.