4.4. SR 03-20-2017 - Laserfiche WebLink

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EXECUTIVE SUMMARY The following Leachate Study is designed to evaluate the impact of landfill leachate on the Elk River treatment processes and alternatives to convey the leachate through the collection system. Completion of a preliminary engineering report is step 1 as outlined in the Memorandum of Understanding between the City of Elk River and Waste Management of Minnesota, Inc. for landfill leachate and municipal biosolids disposal. The study identifies the potential impact on treatment capacity, biological treatment inhibition, and ultraviolet disinfection as well as conveyance options and recommended next steps. Treatment Capacity Current influent flow to the Elk River Wastewater Treatment Facility averages approximately 1.2 million gallons per day (MGD). The proposed 35,000 gallons per day (gpd) leachate discharge will contribute approximately 3 percent of the average daily influent flow which is projected to drop to less than 1 percent when the facility reaches a design average daily flow of 3.98 MGD. Although flow contributions appear to be insignificant, the COD pollutant contribution may exceed the current domestic wastewater carbonaceous biochemical oxygen demand (CBODs) load of approximately 3,000 lb CBOD5/day. The leachate COD concentration increased in 2013 and 2014 with COD spikes as high as 12,500 and 12,800 mg/L. At 35,000 gpd, the associated COD load of approximately 3,700 lb COD/day would have a significant impact on the design treatment capacity of 7,720 lb CBOD5/day. Typical COD values in 2011 and 2012 ranged from 1,500-2,500 mg/L or an estimated COD load of 440-730 lb/day. Nitrogen contributions from the leachate are estimated at 1,100-1,200 mg/L or approximately 3501b/day. This would account for approximately 25 percent of the design influent nitrogen load of 1,360 lb/day. Additional information is recommended regarding the projected trend in COD concentrations and the typical C13OD5:COD ratio in the leachate. City of Elk River, Minnesota —121.109643 Page 1 Elk River/Waste Management Leachate Study Prepared by Bolton & Menk, Inc.