Agenda - Council - 10/08/2019 - Laserfiche WebLink

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Biological Iron, Manganese and Afflffloi Removal Pilot Study CITY OF ONAMIA, MN The City of Onamia obtains its water supply from two groundwater wells, which are both high in iron and manganese. The wells each have iron more than three times higher and manganese two times higher than the United States Environmental Protection Agency (US EPA) Secondary Standards. Additionally, the concentrations of ammonia in Well Nos. 3 and 4 are 2.7 mg/L and 7.2 mg/L, respectively. For comparison, past data collected by Minnesota Department of Health (MDH) suggests that more than 86% of Minnesota wells have ammonia concentrations less than 1.1 mg/L. The abnormally high levels of ammonia are of concern to both the City and MDH due to the higher risk of nitrification in the distribution system and difficulties maintaining a disinfectant residual. SEH was hired by the City to conduct a biological treatment pilot study to remove the ammonia, iron and manganese from their water. City staff is operating the pilot equipment. Recently, the pilot system was able to remove 10 mg/L of ammonia, nearly 50% of the raw water manganese, and iron to well below the 0.3 mg/L secondary standard. REFERENCE Josh True Water System Operator 320.630.6217 SEH TEAM Jeff Ledin I Project Manager Kevin Young I Project Engineer John Thom I Water Operations Specialist Water Treatment Plant CITY OF GIBBON, MN Poor water quality, an aging facility and limited space for expansion resulted in the City of Gibbon opting to design a new water treatment plant (WTP). The City's original WTP was an iron and manganese removal plant with aeration and gravity filtration. The water treatment equipment was housed within the City's jail, which was constructed in the early 1900s. Both the structure and the treatment equipment were in need of significant repairs, with the last major renovation — the rehabilitation of the steel gravity filters — completed more than 20 years prior. SEH team members were involved in the planning design and construction services for a cost-effective concrete gravity filter plant to replace the existing WTP and enhance iron and manganese removal. The plants processes include aeration, concrete gravity filters, sodium hypochlorite feed, potassium permanganate feed, fluoride feed, a clearwell, and high service pumps. The project also included a complete upgrade of the plants SCADA system. Further adding to the complexity of the project, it was necessary for the WTP to fit on an existing single home lot adjacent to the existing water tower to minimize costs and reuse as much existing underground infrastructure as possible. REFERENCE Dana Lietzau City Administrator —City of Gibbon 507.834.6566 SEH TEAM Chris Larson I Project Manager Chad Katzenberger I Project Engineer John Thom I Water Operations Specialist 23 CENTRALIZED WATER TREATMENT FACILITY PROPOSAL