4.4. SR 03-20-2017 - Laserfiche WebLink

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SECTION 4.0 LEACHATE TREATMENT EVALUATION 4.1 General Concerns related to the combined treatment of municipal wastewater and the Elk River Landfill leachate are discussed in the following section. These concerns include 1) corrosion and/or odors in the collection system; 2) hydraulic and organic treatment capacity; 3) inhibition and/or toxicity to the biological treatment processes; 4) effectiveness of the ultraviolet disinfection process; 5) change in biosolids characteristics and quantity; and 6) evaluation of other combined treatment facilities. 4.2 Collection System Concerns Odor and corrosion are two concerns related to discharge of leachate into the Elk River collection system. Corrosion due to low or high pH is not anticipated as the leachate typically remains in the neutral range with observed levels of 7.3-7.6 SU and alkalinity, or pH buffering capacity, of 5,000-8,000 mg/L. Odors may be generated due to oxygen depletion and hydrogen sulfide gas generation in the Waste Management storage tanks and the estimated 10-12 hours in the proposed 4 to 5 mile 4 -in diameter forcemain from the Waste Management facility to the collection system. 4.3 Hydraulic and Organic Treatment Capacity The leachate flow volume is projected to remain consistent at approximately 35,000 gpd. The oxygen demand (chemical oxygen demand (COD)) is anticipated in the range of 5,000- 15,000-mg/L and the total Kjeldahl nitrogen concentration is estimated at 1,100-1,200 mg/L. Waste Management monitors COD rather than CBODs, the COD:CBODs ratio is not known, however COD will always be greater than CBODs. TKN data for leachate is based on two data points in September and November 2014. The COD load at the project flow is estimated at 1,460-4,380 lb/day while the TKN load is estimated at approximately 350 lb N/day. This accounts for approximately 25-35 percent of the design capacity and 50-75 percent of the reserve capacity allocated to future development both in and outside the urban service area. City of'Elk River, Minnesota — T21.109643 Page 14 Elk River/Waste Management Leachate Study Prepared by Bolton & Menk, Inc.