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flow of 35,000 gallons per day are 2,700 lb COD/day and 327 lb TKN/day. Estimated <br />biodegradable fraction, or CBOD5 load, ranges from 270-1,9001b/day. A significant increase in <br />COD concentrations was noted from 2,500 mg/L in 2011 to 9,300 mg/L in 2014. The <br />contributing factors associated with the observed increase are not known. <br />Chloride, mercury, zinc and a few other parameters are present in concentrations that may result <br />in effluent concentrations in excess of associated water quality standards (WQS) depending on <br />the concentrations associated with the municipal load. The dilution ratio provided by the <br />Mississippi river, however, results in only a minor impact on WQS in the receiving stream. <br />Therefore, the existing WWTF effluent concentrations were not reviewed in detail to refine the <br />projected effluent concnetrations. <br />Metal concentrations in the biosolids were also projected based on typical activated sludge <br />removal efficiencies documented in Appendix G of the EPA Local Limits Development <br />Guidance (Appendix E of this report). All biosolids metal concentrations are projected below <br />ceiling concentrations limits, however, zinc concentrations have the potential to impact <br />cumulative loading limit if municipal zinc contributions are not negligible. Biosolids annual and <br />cumulative loading limits do not apply if the biosolids are landfilled at the Waste Management <br />facility. <br />Color is difficult to quantify in analytical terms, however, this is a significant parameter of <br />concern when treating landfill leachate. The Waste Management Elk River Landfill leachate is <br />no exception with an observed dark tinge. Color impacts the aesthetics of the treated effluent <br />and the effectiveness of the UV disinfection process. The transmittance of the wastewater is <br />dramatically reduced by color and the effectiveness of the ultraviolet (UV) disinfection system. <br />City of Elk River, Minnesota —121.109643 Page 13 <br />Elk River/Waste Management Leachate Study Prepared by Bolton & Menk, Inc. <br />