4.4. SR 03-20-2017 - Laserfiche WebLink

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Biological Treatment Evaluation of the treatability of combined municipal wastewater and leachate utilized the Environmental Pollution Agency (EPA) Local Limits Development Guidance. This document provides guidance regarding toxic and inhibitory compounds as well as anticipated removal efficiencies through the typical biological treatment processes. Comparison of the EPA documented inhibition values (Appendix G of Local Limits Development Guidance) and the anticipated blended pollutant concentrations identified only one parameter that approaches the threshold level for inhibition. The reported range of zinc inhibition is 0.3-10 mg/L for activated sludge and 0.08-0.5 mg/L for nitrification. Zinc concentrations in the blended is wastewater are projected at 0.2-0.4 mg/L when only accounting for mass received in the leachate. Zinc would also be a parameter of concern if the biosolids disposal alternative of land application was desired. Complete nitrification of the estimated influent nitrogen concentration of 90-100 mg/L will result in an effluent nitrate concentration in the similar range. If denitrification, (conversion of nitrate to nitrogen gas) is required to meet future total nitrogen limits, supplemental carbon may be required. Future nitrogen limits may be as low as 10 mg/L total nitrogen. Ultraviolet (UV) Disinfection The existing UV disinfection system is designed to achieve a dose of 30,000 µWs/cm2 at a peak design flow of 7.0 MGD and a UV transmittance (UVT) of 61 percent. The landfill leachate has a distinct color that reduces the UVT and effectiveness of the UV disinfection system. A bench scale study evaluated UVT reduction with a combination of raw leachate and treated municipal wastewater. A theoretical impact on UV system performance was calculated based on the measured the UVT values of the blended solutions. This conservative evaluation assumes color in the leachate is not removed through the biological treatment process. Results of the UVT evaluation are summarized below. These results indicate the need for pilot testing with activated sludge treatment as the existing UV disinfection system cannot achieve the design UV dose of 30,000 µWs/cm2 with blended flow of less than 5 MGD. City of Elk River, Minnesota —121.109643 Page 2 Elk River/Waste Management Leachate Study Prepared by Bolton & Menk, Inc.